diff --git a/src/c/compiler.d b/src/c/compiler.d
index de477a188..b5025d3ff 100644
--- a/src/c/compiler.d
+++ b/src/c/compiler.d
@@ -130,7 +130,6 @@ static int c_listA(cl_env_ptr env, cl_object args, int push);
 
 static cl_object ecl_make_lambda(cl_env_ptr env, cl_object name, cl_object lambda);
 
-static void FEillegal_variable_name(cl_object) ecl_attr_noreturn;
 static void FEill_formed_input(void) ecl_attr_noreturn;
 
 /* -------------------- SAFE LIST HANDLING -------------------- */
@@ -343,12 +342,6 @@ assert_type_symbol(cl_object v)
     FEprogram_error_noreturn("Expected a symbol, found ~S.", 1, v);
 }
 
-static void
-FEillegal_variable_name(cl_object v)
-{
-  FEprogram_error_noreturn("Not a valid variable name ~S.", 1, v);
-}
-
 static void
 FEill_formed_input()
 {
diff --git a/src/c/error.d b/src/c/error.d
index 2c42b789c..afe4f0ebd 100644
--- a/src/c/error.d
+++ b/src/c/error.d
@@ -434,6 +434,12 @@ FEinvalid_variable(const char *s, cl_object obj)
   FEerror(s, 1, obj);
 }
 
+void
+FEillegal_variable_name(cl_object v)
+{
+  FEprogram_error("Not a valid variable name ~S.", 1, v);
+}
+
 void
 FEassignment_to_constant(cl_object v)
 {
diff --git a/src/c/stacks.d b/src/c/stacks.d
index 3af6d75d5..e74e7efbd 100644
--- a/src/c/stacks.d
+++ b/src/c/stacks.d
@@ -199,7 +199,7 @@ ecl_progv(cl_env_ptr env, cl_object vars0, cl_object values0)
     } else {
       cl_object var = ECL_CONS_CAR(vars);
       if (!ECL_SYMBOLP(var))
-        FEerror("Not a valid variable name ~S.", 1, var);
+        FEillegal_variable_name(var);
       if (ecl_symbol_type(var) & ecl_stp_constant)
         FEbinding_a_constant(var);
       if (Null(values)) {
diff --git a/src/h/external.h b/src/h/external.h
index f85fb74ae..b5c3dbb3e 100755
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -577,6 +577,7 @@ extern ECL_API void FEwrong_index(cl_object function, cl_object a, int which, cl
 extern ECL_API void FEunbound_variable(cl_object sym) ecl_attr_noreturn;
 extern ECL_API void FEinvalid_macro_call(cl_object obj) ecl_attr_noreturn;
 extern ECL_API void FEinvalid_variable(const char *s, cl_object obj) ecl_attr_noreturn;
+extern ECL_API void FEillegal_variable_name(cl_object) ecl_attr_noreturn;
 extern ECL_API void FEassignment_to_constant(cl_object v) ecl_attr_noreturn;
 extern ECL_API void FEbinding_a_constant(cl_object v) ecl_attr_noreturn;
 extern ECL_API void FEundefined_function(cl_object fname) ecl_attr_noreturn;