diff --git a/harbour/source/pp/ppcore.c b/harbour/source/pp/ppcore.c
index 554a97cb2d..6ef9d568d0 100644
--- a/harbour/source/pp/ppcore.c
+++ b/harbour/source/pp/ppcore.c
@@ -582,7 +582,7 @@ DEFINES * hb_pp_AddDefine( char * defname, char * value )
 
   if( stdef != NULL )
   {
-    if( strcmp(stdef->value, value ) != 0 )
+    if( stdef->value && strcmp(stdef->value, value ) != 0 )
         hb_compGenWarning( hb_pp_szWarnings, 'I', HB_PP_WARN_DEFINE_REDEF, defname, NULL );
 
     if( isNew )