diff --git a/mercurial/bdiff.c b/mercurial/bdiff.c
--- a/mercurial/bdiff.c
+++ b/mercurial/bdiff.c
@@ -95,7 +95,7 @@
 
 	/* try to allocate a large hash table to avoid collisions */
 	for (scale = 4; scale; scale /= 2) {
-		h = (struct pos *)malloc(scale * buckets * sizeof(struct pos));
+		h = (struct pos *)calloc(buckets, scale * sizeof(struct pos));
 		if (h)
 			break;
 	}