diff --git a/xo-interpreter2/src/interpreter2/VirtualSchematikaMachine.cpp b/xo-interpreter2/src/interpreter2/VirtualSchematikaMachine.cpp
index 8807a72c..6bcbe8bf 100644
--- a/xo-interpreter2/src/interpreter2/VirtualSchematikaMachine.cpp
+++ b/xo-interpreter2/src/interpreter2/VirtualSchematikaMachine.cpp
@@ -15,6 +15,7 @@
 #include "VsmRcx.hpp"
 #include "Closure.hpp"
 #include <xo/object2/Sequence.hpp>
+#include <xo/object2/List.hpp>
 #include <xo/numeric/NumericDispatch.hpp>
 #include <xo/expression2/DefineExpr.hpp>
 #include <xo/expression2/ApplyExpr.hpp>
@@ -914,7 +915,7 @@ namespace xo {
         static DPrimitive_gco_0 s_cwd_pm("_cwd",
                                          &xfer_cwd);
 
-        // ----- primitive: fn_nth() -----
+        // ----- primitive: nth() -----
 
         // TODO: seq_gc -> obj<ASequence>
         //       n_gco -> obj<AGCObject,DInteger>
@@ -934,6 +935,24 @@ namespace xo {
 
         static DPrimitive_gco_2_gco_gco s_nth_pm("_nth", &xfer_nth);
 
+        // ----- primitive: cons() -----
+
+        obj<AGCObject>
+        xfer_cons(obj<ARuntimeContext> rcx,
+                  obj<AGCObject> car,
+                  obj<AGCObject> cdr)
+        {
+            (void)rcx;
+
+            auto cdr_list = obj<AGCObject,DList>::from(cdr);
+
+            return DList::cons(rcx.allocator(),
+                               car,
+                               cdr_list.data());
+        }
+
+        static DPrimitive_gco_2_gco_gco s_cons_pm("_cons", &xfer_cons);
+
         // ----- primitive: fn_n_args() -----
 
         obj<AGCObject>
@@ -1038,6 +1057,18 @@ namespace xo {
                      obj<AGCObject,DPrimitive_gco_2_gco_gco>(&s_nth_pm));
             }
 
+            /* cons */
+            {
+                const DUniqueString * name
+                    = reader_.intern_string("cons");
+
+                global_env_->_upsert_value
+                    (mm_.to_op(),
+                     name,
+                     Reflect::require<DPrimitive_gco_2_gco_gco>(),
+                     obj<AGCObject,DPrimitive_gco_2_gco_gco>(&s_cons_pm));
+            }
+
             /* fn_n_args */
             {
                 const DUniqueString * name
diff --git a/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp b/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
index 21b5faa3..9fb85ffc 100644
--- a/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
+++ b/xo-interpreter2/utest/VirtualSchematikaMachine.test.cpp
@@ -31,7 +31,7 @@ namespace xo {
     using xo::scm::DFloat;
     using xo::scm::DBoolean;
     using xo::scm::DInteger;
-    using xo::scm::DRuntimeError;
+//    using xo::scm::DRuntimeError;
     using xo::mm::AGCObject;
     using xo::mm::MemorySizeInfo;
     using xo::mm::AAllocator;
diff --git a/xo-object2/include/xo/object2/DList.hpp b/xo-object2/include/xo/object2/DList.hpp
index 01ef3eb6..8009f7b5 100644
--- a/xo-object2/include/xo/object2/DList.hpp
+++ b/xo-object2/include/xo/object2/DList.hpp
@@ -26,11 +26,14 @@ namespace xo {
             DList(xo::obj<AGCObject> h,
                   DList * r) : head_{h}, rest_{r} {}
 
-            /** sentinel for null list.
+            /** sentinel for null list.  Idempotent.
              *  Application code may prefer ListOps::nil()
              **/
             static DList * _nil();
 
+            /** like _nil(), but retrn fop wrapper **/
+            static obj<AGCObject,DList> nil();
+
             /** list with first element @p car,
              *  followed by contents of list @p cdr.
              *  Shares structure with @p cdr
@@ -40,6 +43,11 @@ namespace xo {
                                  obj<AGCObject> car,
                                  DList * cdr);
 
+            /** like @c _cons(mm,car,cdr), but return fop wrapper **/
+            static obj<AGCObject,DList> cons(obj<AAllocator> mm,
+                                             obj<AGCObject> car,
+                                             DList * cdr);
+
             /** DList length is at least 1 **/
             bool is_empty() const noexcept;
             /** DList models a finite sequence **/
diff --git a/xo-object2/src/object2/DList.cpp b/xo-object2/src/object2/DList.cpp
index 25770d01..7ef06f36 100644
--- a/xo-object2/src/object2/DList.cpp
+++ b/xo-object2/src/object2/DList.cpp
@@ -17,7 +17,7 @@ namespace xo {
     using xo::print::APrintable;
     using xo::mm::AGCObject;
     using xo::facet::FacetRegistry;
-    using xo::facet::typeseq;
+    //using xo::facet::typeseq;
 
     namespace scm {
         static DList s_null(obj<AGCObject>(), nullptr);
@@ -28,6 +28,12 @@ namespace xo {
             return &s_null;
         }
 
+        obj<AGCObject,DList>
+        DList::nil()
+        {
+            return obj<AGCObject,DList>(_nil());
+        }
+
         DList *
         DList::_cons(obj<AAllocator> mm,
                      obj<AGCObject> car,
@@ -38,6 +44,14 @@ namespace xo {
             return new (mem) DList(car, cdr);
         }
 
+        obj<AGCObject,DList>
+        DList::cons(obj<AAllocator> mm,
+                    obj<AGCObject> car,
+                    DList * cdr)
+        {
+            return obj<AGCObject,DList>(_cons(mm, car, cdr));
+        }
+
 #ifdef OBSOLETE
         DList *
         DList::list(obj<AAllocator> mm,
@@ -137,8 +151,6 @@ namespace xo {
                     obj<APrintable> elt
                         = FacetRegistry::instance().variant<APrintable, AGCObject>(l->head_);
 
-
-
                     assert(elt.data());
 
                     if (!pps->print_upto(elt))
diff --git a/xo-reader2/include/xo/reader2/DExpectExprSsm.hpp b/xo-reader2/include/xo/reader2/DExpectExprSsm.hpp
index 539fbb39..66189754 100644
--- a/xo-reader2/include/xo/reader2/DExpectExprSsm.hpp
+++ b/xo-reader2/include/xo/reader2/DExpectExprSsm.hpp
@@ -84,12 +84,18 @@ namespace xo {
             void on_quote_token(const Token & tk,
                                 ParserStateMachine * p_psm);
 
-            /** step state machine for this syntax on incoming boolean literal token @p tkk
+            /** step state machine for this syntax on incoming boolean literal token @p tk
              *  with overall parser state in @p p_psm
              **/
             void on_bool_token(const Token & tk,
                                ParserStateMachine * p_psm);
 
+            /** step state machine for this syntax on incoming nil literal token @p tk
+             *  with overall parser state in @p p_psm.
+             **/
+            void on_nil_token(const Token & tk,
+                              ParserStateMachine * p_psm);
+
             /** update state for this syntax on incoming f64 token @p tk,
              *  overall parser state in @p p_psm
              **/
diff --git a/xo-reader2/include/xo/reader2/DToplevelSeqSsm.hpp b/xo-reader2/include/xo/reader2/DToplevelSeqSsm.hpp
index 9bb9b076..2466ed1e 100644
--- a/xo-reader2/include/xo/reader2/DToplevelSeqSsm.hpp
+++ b/xo-reader2/include/xo/reader2/DToplevelSeqSsm.hpp
@@ -119,6 +119,11 @@ namespace xo {
              **/
             void on_bool_token(const Token & tk, ParserStateMachine * p_psm);
 
+            /** update state for this syntax on incoming nil token @p tk,
+             *  overall parser state in @p p_psm
+             **/
+            void on_nil_token(const Token & tk, ParserStateMachine * p_psm);
+
             /** update state for this syntax on incoming leftparen token @p tk,
              *  overall parser state in @p p_psm
              **/
diff --git a/xo-reader2/src/reader2/DApplySsm.cpp b/xo-reader2/src/reader2/DApplySsm.cpp
index ad9a4e50..cd591c9c 100644
--- a/xo-reader2/src/reader2/DApplySsm.cpp
+++ b/xo-reader2/src/reader2/DApplySsm.cpp
@@ -171,6 +171,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_let:
diff --git a/xo-reader2/src/reader2/DDefineSsm.cpp b/xo-reader2/src/reader2/DDefineSsm.cpp
index 344e1fc1..2f7f99be 100644
--- a/xo-reader2/src/reader2/DDefineSsm.cpp
+++ b/xo-reader2/src/reader2/DDefineSsm.cpp
@@ -546,6 +546,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DDeftypeSsm.cpp b/xo-reader2/src/reader2/DDeftypeSsm.cpp
index ec36391a..383f4fee 100644
--- a/xo-reader2/src/reader2/DDeftypeSsm.cpp
+++ b/xo-reader2/src/reader2/DDeftypeSsm.cpp
@@ -150,6 +150,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DExpectExprSsm.cpp b/xo-reader2/src/reader2/DExpectExprSsm.cpp
index c2d46140..f4fabfc9 100644
--- a/xo-reader2/src/reader2/DExpectExprSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectExprSsm.cpp
@@ -18,6 +18,7 @@
 #include <xo/object2/Boolean.hpp>
 #include <xo/object2/Integer.hpp>
 #include <xo/object2/Float.hpp>
+#include <xo/object2/List.hpp>
 #include <xo/stringtable2/String.hpp>
 #include <xo/alloc2/GCObject.hpp>
 #include <xo/facet/facet_implementation.hpp>
@@ -155,6 +156,10 @@ namespace xo {
                 this->on_bool_token(tk, p_psm);
                 return;
 
+            case tokentype::tk_nil:
+                this->on_nil_token(tk, p_psm);
+                return;
+
             case tokentype::tk_if:
                 this->on_if_token(tk, p_psm);
                 return;
@@ -372,6 +377,23 @@ namespace xo {
                                 p_psm);
         }
 
+        void
+        DExpectExprSsm::on_nil_token(const Token & tk,
+                                     ParserStateMachine * p_psm)
+        {
+            (void)tk;
+
+            auto nil = DList::nil();
+            auto expr = DConstant::make(p_psm->expr_alloc(), nil);
+
+            // DProgressSsm responsible for resolving cases like
+            //   nil ++ nil;
+
+            DProgressSsm::start(p_psm->parser_alloc(),
+                                expr,
+                                p_psm);
+        }
+
         void
         DExpectExprSsm::on_f64_token(const Token & tk,
                                      ParserStateMachine * p_psm)
diff --git a/xo-reader2/src/reader2/DExpectFormalArgSsm.cpp b/xo-reader2/src/reader2/DExpectFormalArgSsm.cpp
index db287abf..a17d094c 100644
--- a/xo-reader2/src/reader2/DExpectFormalArgSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectFormalArgSsm.cpp
@@ -135,6 +135,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DExpectFormalArglistSsm.cpp b/xo-reader2/src/reader2/DExpectFormalArglistSsm.cpp
index 67f327e1..9f7da033 100644
--- a/xo-reader2/src/reader2/DExpectFormalArglistSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectFormalArglistSsm.cpp
@@ -165,6 +165,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DExpectListTypeSsm.cpp b/xo-reader2/src/reader2/DExpectListTypeSsm.cpp
index 3b040962..1f42d171 100644
--- a/xo-reader2/src/reader2/DExpectListTypeSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectListTypeSsm.cpp
@@ -127,6 +127,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DExpectQArraySsm.cpp b/xo-reader2/src/reader2/DExpectQArraySsm.cpp
index 33ccd7c8..aa89862f 100644
--- a/xo-reader2/src/reader2/DExpectQArraySsm.cpp
+++ b/xo-reader2/src/reader2/DExpectQArraySsm.cpp
@@ -122,6 +122,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DExpectQListSsm.cpp b/xo-reader2/src/reader2/DExpectQListSsm.cpp
index 9584bfea..f3f50b81 100644
--- a/xo-reader2/src/reader2/DExpectQListSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectQListSsm.cpp
@@ -122,6 +122,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DExpectQLiteralSsm.cpp b/xo-reader2/src/reader2/DExpectQLiteralSsm.cpp
index 92309ddc..4cb26099 100644
--- a/xo-reader2/src/reader2/DExpectQLiteralSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectQLiteralSsm.cpp
@@ -140,6 +140,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DExpectSymbolSsm.cpp b/xo-reader2/src/reader2/DExpectSymbolSsm.cpp
index 79ae0622..17cdca06 100644
--- a/xo-reader2/src/reader2/DExpectSymbolSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectSymbolSsm.cpp
@@ -101,6 +101,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DExpectTypeSsm.cpp b/xo-reader2/src/reader2/DExpectTypeSsm.cpp
index 600b7650..9eb2b15d 100644
--- a/xo-reader2/src/reader2/DExpectTypeSsm.cpp
+++ b/xo-reader2/src/reader2/DExpectTypeSsm.cpp
@@ -107,6 +107,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DIfElseSsm.cpp b/xo-reader2/src/reader2/DIfElseSsm.cpp
index 5752dbdc..b915c061 100644
--- a/xo-reader2/src/reader2/DIfElseSsm.cpp
+++ b/xo-reader2/src/reader2/DIfElseSsm.cpp
@@ -186,6 +186,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_let:
diff --git a/xo-reader2/src/reader2/DLambdaSsm.cpp b/xo-reader2/src/reader2/DLambdaSsm.cpp
index 9364476a..ac19c7e0 100644
--- a/xo-reader2/src/reader2/DLambdaSsm.cpp
+++ b/xo-reader2/src/reader2/DLambdaSsm.cpp
@@ -163,6 +163,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_then:
             case tokentype::tk_else:
diff --git a/xo-reader2/src/reader2/DParenSsm.cpp b/xo-reader2/src/reader2/DParenSsm.cpp
index d3fb5cfa..7bf28d02 100644
--- a/xo-reader2/src/reader2/DParenSsm.cpp
+++ b/xo-reader2/src/reader2/DParenSsm.cpp
@@ -132,6 +132,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DProgressSsm.cpp b/xo-reader2/src/reader2/DProgressSsm.cpp
index edb55001..be927bef 100644
--- a/xo-reader2/src/reader2/DProgressSsm.cpp
+++ b/xo-reader2/src/reader2/DProgressSsm.cpp
@@ -309,6 +309,7 @@ namespace xo {
                 this->on_operator_token(tk, p_psm);
                 return;
 
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
                 break;
diff --git a/xo-reader2/src/reader2/DQuoteSsm.cpp b/xo-reader2/src/reader2/DQuoteSsm.cpp
index 7f6dd00d..c61ed632 100644
--- a/xo-reader2/src/reader2/DQuoteSsm.cpp
+++ b/xo-reader2/src/reader2/DQuoteSsm.cpp
@@ -133,6 +133,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_then:
diff --git a/xo-reader2/src/reader2/DSequenceSsm.cpp b/xo-reader2/src/reader2/DSequenceSsm.cpp
index 8bb2f779..b2b237dd 100644
--- a/xo-reader2/src/reader2/DSequenceSsm.cpp
+++ b/xo-reader2/src/reader2/DSequenceSsm.cpp
@@ -114,6 +114,7 @@ namespace xo {
             case tokentype::tk_slash:
             case tokentype::tk_cmpeq:
             case tokentype::tk_cmpne:
+            case tokentype::tk_nil:
             case tokentype::tk_type:
             case tokentype::tk_lambda:
             case tokentype::tk_let:
diff --git a/xo-reader2/src/reader2/DToplevelSeqSsm.cpp b/xo-reader2/src/reader2/DToplevelSeqSsm.cpp
index 2b5b0dcb..612f64fd 100644
--- a/xo-reader2/src/reader2/DToplevelSeqSsm.cpp
+++ b/xo-reader2/src/reader2/DToplevelSeqSsm.cpp
@@ -17,6 +17,7 @@
 
 #include <xo/expression2/Constant.hpp>
 #include <xo/stringtable2/String.hpp>
+#include <xo/object2/List.hpp>
 #include <xo/object2/Float.hpp>
 #include <xo/object2/Integer.hpp>
 #include <xo/object2/Boolean.hpp>
@@ -152,6 +153,10 @@ namespace xo {
                 this->on_bool_token(tk, p_psm);
                 return;
 
+            case tokentype::tk_nil:
+                this->on_nil_token(tk, p_psm);
+                return;
+
             case tokentype::tk_leftparen:
                 this->on_leftparen_token(tk, p_psm);
                 return;
@@ -378,7 +383,7 @@ namespace xo {
                 break;
             }
 
-            Super::on_token(tk, p_psm);
+            Super::illegal_token(tk, p_psm);
         }
 
         void
@@ -404,7 +409,32 @@ namespace xo {
                 break;
             }
 
-            Super::on_token(tk, p_psm);
+            Super::illegal_token(tk, p_psm);
+        }
+
+        void
+        DToplevelSeqSsm::on_nil_token(const Token & tk,
+                                      ParserStateMachine * p_psm)
+        {
+            switch (seqtype_) {
+            case exprseqtype::toplevel_interactive:
+            {
+                auto dvalue = DList::nil();
+                auto expr = DConstant::make(p_psm->expr_alloc(), dvalue);
+
+                DProgressSsm::start(p_psm->parser_alloc(),
+                                    expr,
+                                    p_psm);
+                return;
+            }
+            case exprseqtype::toplevel_batch:
+                break;
+            case exprseqtype::N:
+                assert(false);
+                break;
+            }
+
+            Super::illegal_token(tk, p_psm);
         }
 
         void
@@ -431,7 +461,7 @@ namespace xo {
                 break;
             }
 
-            Super::on_token(tk, p_psm);
+            Super::illegal_token(tk, p_psm);
         }
 
         void
@@ -454,7 +484,7 @@ namespace xo {
                 break;
             }
 
-            Super::on_token(tk, p_psm);
+            Super::illegal_token(tk, p_psm);
         }
 
         void
diff --git a/xo-reader2/utest/SchematikaParser.test.cpp b/xo-reader2/utest/SchematikaParser.test.cpp
index 0b1fea58..6f97d7a0 100644
--- a/xo-reader2/utest/SchematikaParser.test.cpp
+++ b/xo-reader2/utest/SchematikaParser.test.cpp
@@ -15,6 +15,7 @@
 #include <xo/expression2/VarRef.hpp>
 #include <xo/expression2/Constant.hpp>
 #include <xo/procedure2/Primitive_gco_2_gco_gco.hpp>
+#include <xo/object2/List.hpp>
 #include <xo/object2/Float.hpp>
 #include <xo/object2/Integer.hpp>
 #include <xo/stringtable2/String.hpp>
@@ -41,6 +42,7 @@ namespace xo {
     using xo::scm::Token;
     using xo::mm::AGCObject;
     using xo::scm::DPrimitive_gco_2_gco_gco;
+    using xo::scm::DList;
     using xo::scm::DString;
     using xo::scm::DFloat;
     using xo::scm::DInteger;
@@ -603,6 +605,67 @@ namespace xo {
             log && fixture.log_memory_layout(&log);
         }
 
+        TEST_CASE("SchematikaParser-interactive-nil", "[reader2][SchematikaParser]")
+        {
+            const auto & testname = Catch::getResultCapture().getCurrentTestName();
+
+            constexpr bool c_debug_flag = false;
+            scope log(XO_DEBUG(c_debug_flag), xtag("test", testname));
+
+            ParserFixture fixture(testname, c_debug_flag);
+            auto & parser = *(fixture.parser_);
+
+            parser.begin_interactive_session();
+
+            /** Walkthrough parsing input equivalent to:
+             *
+             *    nil ;
+             *
+             **/
+
+            {
+                auto & result = parser.on_token(Token::nil_token());
+
+                log && log("after nil token:");
+                log && log(xtag("parser", &parser));
+                log && log(xtag("result", result));
+
+                REQUIRE(parser.has_incomplete_expr() == true);
+                REQUIRE(!result.is_error());
+                REQUIRE(result.is_incomplete());
+            }
+
+            {
+                auto & result = parser.on_token(Token::semicolon_token());
+
+                log && log("after semicolon token:");
+                log && log(xtag("parser", &parser));
+                log && log(xtag("result", result));
+
+                REQUIRE(parser.has_incomplete_expr() == false);
+                REQUIRE(!result.is_error());
+                REQUIRE(result.is_expression());
+                REQUIRE(result.result_expr());
+
+                auto expr = obj<AExpression,DConstant>::from(result.result_expr());
+                REQUIRE(expr);
+
+                REQUIRE(expr->value());
+
+                auto value_list = obj<AGCObject,DList>::from(expr->value());
+
+                REQUIRE(value_list);
+
+                REQUIRE(value_list->is_empty());
+            }
+
+            //REQUIRE(result.is_error());
+            //// illegal input on token
+            //REQUIRE(result.error_description());
+
+            log && fixture.log_memory_layout(&log);
+        }
+
         TEST_CASE("SchematikaParser-interactive-arith", "[reader2][SchematikaParser]")
         {
             const auto & testname = Catch::getResultCapture().getCurrentTestName();
diff --git a/xo-tokenizer2/include/xo/tokenizer2/Token.hpp b/xo-tokenizer2/include/xo/tokenizer2/Token.hpp
index 7537a2b0..0968a9e9 100644
--- a/xo-tokenizer2/include/xo/tokenizer2/Token.hpp
+++ b/xo-tokenizer2/include/xo/tokenizer2/Token.hpp
@@ -134,6 +134,8 @@ namespace xo {
             /** token for @c "==" **/
             static Token cmpeq_token() { return Token(tokentype::tk_cmpeq); }
 
+            /** token representing keyword @c nil **/
+            static Token nil_token() { return Token(tokentype::tk_nil); }
             /** token representing keyword @c type **/
             static Token type() { return Token(tokentype::tk_type); }
             /** token representing keyword @c def **/
diff --git a/xo-tokenizer2/include/xo/tokenizer2/tokentype.hpp b/xo-tokenizer2/include/xo/tokenizer2/tokentype.hpp
index d0290b05..5f7e1937 100644
--- a/xo-tokenizer2/include/xo/tokenizer2/tokentype.hpp
+++ b/xo-tokenizer2/include/xo/tokenizer2/tokentype.hpp
@@ -140,6 +140,9 @@ namespace xo {
             /** operator @c '!=' **/
             tk_cmpne,
 
+            /** keyword @c 'nil' **/
+            tk_nil,
+
             /** keyword @c 'type' **/
             tk_type,
 
diff --git a/xo-tokenizer2/src/tokenizer2/Tokenizer.cpp b/xo-tokenizer2/src/tokenizer2/Tokenizer.cpp
index f6ac7c2f..2a6f8ed9 100644
--- a/xo-tokenizer2/src/tokenizer2/Tokenizer.cpp
+++ b/xo-tokenizer2/src/tokenizer2/Tokenizer.cpp
@@ -587,6 +587,8 @@ namespace xo {
                 if ((tk_text == "true") || (tk_text == "false")) {
                     tk_type = tokentype::tk_bool;
                     keep_text = true;
+                } else if (tk_text == "nil") {
+                    tk_type = tokentype::tk_nil;
                 } else if (tk_text == "type") {
                     tk_type = tokentype::tk_type;
                 } else if (tk_text == "def") {
diff --git a/xo-tokenizer2/src/tokenizer2/tokentype.cpp b/xo-tokenizer2/src/tokenizer2/tokentype.cpp
index 7df59eec..b8a013da 100644
--- a/xo-tokenizer2/src/tokenizer2/tokentype.cpp
+++ b/xo-tokenizer2/src/tokenizer2/tokentype.cpp
@@ -49,6 +49,7 @@ namespace xo {
                 CASE(tk_cmpeq);
                 CASE(tk_cmpne);
 
+                CASE(tk_nil);
                 CASE(tk_type);
                 CASE(tk_def);
                 CASE(tk_deftype);