diff --git a/ivlpp/lexor.lex b/ivlpp/lexor.lex
index b8ccb6296..a74a8c357 100644
--- a/ivlpp/lexor.lex
+++ b/ivlpp/lexor.lex
@@ -860,16 +860,17 @@ void define_macro(const char* name, const char* value, int keyword, int argc)
     struct define_t* def;
     struct define_t* prev;
 
-    /* Verilog spec has a very nasty system of macros jumping from
-     * file to file, resulting in a global macro scope. We abosolutely
-     * MUST track macro redefinitions and warn user about them.
+    /* Verilog has a very nasty system of macros jumping from
+     * file to file, resulting in a global macro scope. Here
+     * we optionally warn about any redefinitions.
      */
-
-    prev = def_lookup(name);
-    if (prev && warn_redef) {
-        emit_pathline(istack);
-        fprintf(stderr, "warning: redefinition of macro %s from value '%s' to '%s'\n",
-            name, prev->value, value);
+    if (warn_redef) {
+	prev = def_lookup(name);
+	if (prev) {
+	    emit_pathline(istack);
+	    fprintf(stderr, "warning: redefinition of macro %s from value '%s' to '%s'\n",
+	    name, prev->value, value);
+	}
     }
 
     def = malloc(sizeof(struct define_t));