diff --git a/mercurial/cext/manifest.c b/mercurial/cext/manifest.c
--- a/mercurial/cext/manifest.c
+++ b/mercurial/cext/manifest.c
@@ -185,7 +185,7 @@ static void lazymanifest_dealloc(lazyman
 {
 	/* free any extra lines we had to allocate */
 	int i;
-	for (i = 0; i < self->numlines; i++) {
+	for (i = 0; self->lines && (i < self->numlines); i++) {
 		if (self->lines[i].from_malloc) {
 			free(self->lines[i].start);
 		}