diff --git a/xo-object2/include/xo/object2/DList.hpp b/xo-object2/include/xo/object2/DList.hpp
index 8009f7b5..ddc54f3f 100644
--- a/xo-object2/include/xo/object2/DList.hpp
+++ b/xo-object2/include/xo/object2/DList.hpp
@@ -57,6 +57,8 @@ namespace xo {
             /** return element at 0-based index @p ix **/
             obj<AGCObject> at(size_type ix) const;
 
+            /** assign head **/
+            void assign_head(obj<ACollector> gc, obj<AGCObject> h);
             /** assign rest-pointer **/
             void assign_rest(DList * r);
 
diff --git a/xo-object2/src/object2/DList.cpp b/xo-object2/src/object2/DList.cpp
index 7ef06f36..b9ac0583 100644
--- a/xo-object2/src/object2/DList.cpp
+++ b/xo-object2/src/object2/DList.cpp
@@ -119,6 +119,14 @@ namespace xo {
             return l->head_;
         }
 
+        void
+        DList::assign_head(obj<ACollector> gc, obj<AGCObject> rhs)
+        {
+            scope log(XO_DEBUG(true), xtag("gc.data", gc.data_));
+
+            mm_do_assign(gc, this, &head_, rhs);
+        }
+
         void
         DList::assign_rest(DList * r)
         {
diff --git a/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp b/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
index c403dc17..87a80457 100644
--- a/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
+++ b/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
@@ -35,6 +35,10 @@ namespace xo {
             static DPrimitive_gco_2_gco_gco * make_cons_pm(obj<AAllocator> mm,
                                                            StringTable * stbl);
 
+            /** create primitive: set first member of cons cell **/
+            static DPrimitive_gco_2_gco_gco * make_set_car_pm(obj<AAllocator> mm,
+                                                              StringTable * stbl);
+
             /** create primitive for creating a dictionary instance **/
             static DPrimitive_gco_0 * make_dict_make_pm(obj<AAllocator> mm,
                                                         StringTable * stbl);
diff --git a/xo-procedure2/src/procedure2/ObjectPrimitives.cpp b/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
index d9d86f4a..36dd2a37 100644
--- a/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
+++ b/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
@@ -116,6 +116,48 @@ namespace xo {
             return DPrimitive_gco_2_gco_gco::_make(mm, "cons", cons_ty, &xfer_cons);
         }
 
+        // ----- set-car -----
+
+        obj<AGCObject>
+        xfer_set_car(obj<ARuntimeContext> rcx,
+                     obj<AGCObject> cell_arg,
+                     obj<AGCObject> dest)
+        {
+            scope log(XO_DEBUG(true));
+
+            (void)rcx;
+            (void)dest;
+
+            auto cell = obj<AGCObject,DList>::from(cell_arg);
+
+            assert(!cell->is_empty());
+
+            if (!cell->is_empty()) {
+                cell->assign_head(rcx.collector(), dest);
+            }
+
+            return cell;
+        }
+
+        DPrimitive_gco_2_gco_gco *
+        ObjectPrimitives::make_set_car_pm(obj<AAllocator> mm,
+                                          StringTable * stbl)
+        {
+            (void)stbl;
+
+            auto any_ty = DAtomicType::make(mm, Metatype::t_any());
+            auto T_ty = DTypeVarRef::make(mm, stbl->intern("T"));
+            auto list_T_ty = DListType::make(mm, T_ty);
+            /** pm_ty: list<T> x any -> list<T> **/
+            auto pm_ty
+                = obj<AType,DFunctionType>(DFunctionType::_make(mm,
+                                                                list_T_ty,
+                                                                any_ty,
+                                                                list_T_ty));
+
+            return DPrimitive_gco_2_gco_gco::_make(mm, "set-car", pm_ty, &xfer_set_car);
+        }
+
         // ----- dict_make -----
 
         obj<AGCObject>
@@ -233,6 +275,7 @@ namespace xo {
         xfer_fn_n_args(obj<ARuntimeContext> rcx,
                        obj<AGCObject> fn_gco)
         {
+
             scope log(XO_DEBUG(true));
 
             log && log(xtag("fn_gco.tseq", fn_gco._typeseq()));