diff --git a/src/interpret_functions.h b/src/interpret_functions.h
index 9b996e9a4e72e82e89c11feea9ac4e77a1573908..f07cc27784971510d1422793f18fc19fc6c04c8e 100644
--- a/src/interpret_functions.h
+++ b/src/interpret_functions.h
@@ -2568,7 +2568,7 @@ OPCODE1(F_LTOSVAL_CALL_BUILTIN_AND_ASSIGN_POP,
   new_frame->args = args;						\
   new_frame->locals=new_frame->save_sp=new_frame->expendible=Pike_sp-args; \
   new_frame->save_mark_sp = new_frame->mark_sp_base = Pike_mark_sp;	   \
-									   \
+  DO_IF_DEBUG(new_frame->num_args=0;new_frame->num_locals=0;);             \
   SET_PROG_COUNTER(addr);						   \
   new_frame->fun=Pike_fp->fun;						   \
   DO_IF_PROFILING( new_frame->ident=Pike_fp->ident );			   \