diff --git a/src/util.c b/src/util.c
index 4f846db..c25baa0 100644
--- a/src/util.c
+++ b/src/util.c
@@ -140,8 +140,8 @@ int ptr_vector_append(struct ptr_vector *vec, void *p) {
 			vec->capacity *= 2;
 		ps = realloc(vec->ptrs, vec->capacity * sizeof(void *));
 		assert(ps != NULL);
-		memset(vec->ptrs + oldcap, 0, (vec->capacity - oldcap) * sizeof(void *));
 		vec->ptrs = ps;
+		memset(vec->ptrs + oldcap, 0, (vec->capacity - oldcap) * sizeof(void *));
 	}
 	vec->ptrs[vec->len] = p;
 	++vec->len;