diff --git a/lib/portableproplib/prop_object.c b/lib/portableproplib/prop_object.c
index 7a2c55af..fab7f555 100644
--- a/lib/portableproplib/prop_object.c
+++ b/lib/portableproplib/prop_object.c
@@ -918,7 +918,7 @@ _prop_object_internalize_map_file(const char *fname)
 		return (NULL);
 	}
 	mf->poimf_mapsize = ((size_t)sb.st_size + pgmask) & ~pgmask;
-	if (mf->poimf_mapsize < sb.st_size) {
+	if (mf->poimf_mapsize < (size_t)sb.st_size) {
 		(void) close(fd);
 		_PROP_FREE(mf, M_TEMP);
 		return (NULL);