diff --git a/include/xo/reader/exprstate.hpp b/include/xo/reader/exprstate.hpp
index 943b70bc..467d2eab 100644
--- a/include/xo/reader/exprstate.hpp
+++ b/include/xo/reader/exprstate.hpp
@@ -126,7 +126,9 @@ namespace xo {
 
             // ----- input methods -----
 
-            virtual void on_def(exprstatestack * p_stack);
+            /** handle incoming 'def' token **/
+            virtual void on_def_token(const token_type & tk,
+                                      exprstatestack * p_stack);
             /** handle incoming symbol token **/
             virtual void on_symbol_token(const token_type & tk,
                                          exprstatestack * p_stack,
diff --git a/include/xo/reader/paren_xs.hpp b/include/xo/reader/paren_xs.hpp
index 8bf137b5..5992837a 100644
--- a/include/xo/reader/paren_xs.hpp
+++ b/include/xo/reader/paren_xs.hpp
@@ -40,9 +40,6 @@ namespace xo {
             virtual bool admits_rightparen() const override;
             virtual bool admits_f64() const override;
 
-            // virtual void on_f64(..) override
-            virtual void on_def(exprstatestack * p_stack) override;
-
             virtual void on_expr(ref::brw<Expression> expr,
                                  exprstatestack * p_stack,
                                  rp<Expression> * p_emit_expr) override;
@@ -53,6 +50,8 @@ namespace xo {
                                       exprstatestack * /*p_stack*/,
                                       rp<Expression> * /*p_emit_expr*/) override;
 
+            virtual void on_def_token(const token_type & tk,
+                                      exprstatestack * p_stack) override;
             virtual void on_symbol_token(const token_type & tk,
                                          exprstatestack * p_stack,
                                          rp<Expression> * p_emit_expr) override;
diff --git a/include/xo/reader/progress_xs.hpp b/include/xo/reader/progress_xs.hpp
index 3203a274..0a0516cf 100644
--- a/include/xo/reader/progress_xs.hpp
+++ b/include/xo/reader/progress_xs.hpp
@@ -31,9 +31,6 @@ namespace xo {
             virtual bool admits_rightparen() const override;
             virtual bool admits_f64() const override;
 
-            // virtual void on_f64(..) override
-            virtual void on_def(exprstatestack * p_stack) override;
-
             virtual void on_expr(ref::brw<Expression> expr,
                                  exprstatestack * p_stack,
                                  rp<Expression> * p_emit_expr) override;
@@ -43,6 +40,9 @@ namespace xo {
             virtual void on_typedescr(TypeDescr td,
                                       exprstatestack * /*p_stack*/,
                                       rp<Expression> * /*p_emit_expr*/) override;
+
+            virtual void on_def_token(const token_type & tk,
+                                      exprstatestack * p_stack) override;
             virtual void on_colon_token(const token_type & tk,
                                         exprstatestack * p_stack) override;
             virtual void on_semicolon_token(const token_type & tk,
diff --git a/src/reader/exprstate.cpp b/src/reader/exprstate.cpp
index 1a33a503..5227135c 100644
--- a/src/reader/exprstate.cpp
+++ b/src/reader/exprstate.cpp
@@ -320,7 +320,8 @@ namespace xo {
         }
 
         void
-        exprstate::on_def(exprstatestack * p_stack) {
+        exprstate::on_def_token(const token_type & /*tk*/,
+                                exprstatestack * p_stack) {
             constexpr bool c_debug_flag = true;
             scope log(XO_DEBUG(c_debug_flag));
 
@@ -652,7 +653,7 @@ namespace xo {
             switch (tk.tk_type()) {
 
             case tokentype::tk_def:
-                this->on_def(p_stack);
+                this->on_def_token(tk, p_stack);
                 return;
 
             case tokentype::tk_i64:
diff --git a/src/reader/paren_xs.cpp b/src/reader/paren_xs.cpp
index 5446cccb..20d7573d 100644
--- a/src/reader/paren_xs.cpp
+++ b/src/reader/paren_xs.cpp
@@ -73,7 +73,9 @@ namespace xo {
         }
 
         void
-        paren_xs::on_def(exprstatestack * /*p_stack*/) {
+        paren_xs::on_def_token(const token_type & /*tk*/,
+                               exprstatestack * /*p_stack*/)
+        {
             constexpr const char * c_self_name = "paren_xs::on_def";
 
             throw std::runtime_error(tostr(c_self_name,
diff --git a/src/reader/progress_xs.cpp b/src/reader/progress_xs.cpp
index bb51cf02..19df5489 100644
--- a/src/reader/progress_xs.cpp
+++ b/src/reader/progress_xs.cpp
@@ -43,7 +43,9 @@ namespace xo {
         progress_xs::admits_f64() const { return false; }
 
         void
-        progress_xs::on_def(exprstatestack * /*p_stack*/) {
+        progress_xs::on_def_token(const token_type & /*tk*/,
+                                  exprstatestack * /*p_stack*/)
+        {
             constexpr const char * self_name = "progress_xs::on_def";
 
             /* nothing here - admits_definition unconditionally false */