diff --git a/pb_decode.c b/pb_decode.c
index 96e0c43..7c68b5a 100644
--- a/pb_decode.c
+++ b/pb_decode.c
@@ -226,7 +226,7 @@ void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream)
 {
     stream->state = substream->state;
 
-#ifdef PB_NO_ERRMSG
+#ifndef PB_NO_ERRMSG
     stream->errmsg = substream->errmsg;
 #endif
 }