diff --git a/programs/util/pem2der.c b/programs/util/pem2der.c
index 5386fdb..dfd7a49 100644
--- a/programs/util/pem2der.c
+++ b/programs/util/pem2der.c
@@ -134,6 +134,7 @@
     {
         fclose( f );
         free( *buf );
+        *buf = NULL;
         return( -1 );
     }