diff --git a/darwin/alloc.m b/darwin/alloc.m
index e271b90e..0bbb8996 100644
--- a/darwin/alloc.m
+++ b/darwin/alloc.m
@@ -71,7 +71,7 @@ void *uiRealloc(void *p, size_t new, const char *type)
 		abort();
 	}
 	s = SIZE(out);
-	if (new <= *s)
+	if (new > *s)
 		memset(((uint8_t *) DATA(out)) + *s, 0, new - *s);
 	*s = new;
 	[allocations removeObject:[NSValue valueWithPointer:p]];
diff --git a/unix/alloc.c b/unix/alloc.c
index 2561efa6..0291bd49 100644
--- a/unix/alloc.c
+++ b/unix/alloc.c
@@ -64,7 +64,7 @@ void *uiRealloc(void *p, size_t new, const char *type)
 	p = BASE(p);
 	out = g_realloc(p, EXTRA + new);
 	s = SIZE(out);
-	if (new <= *s)
+	if (new > *s)
 		memset(((uint8_t *) DATA(out)) + *s, 0, new - *s);
 	*s = new;
 	if (g_ptr_array_remove(allocations, p) == FALSE)
diff --git a/windows/alloc.cpp b/windows/alloc.cpp
index eeee3ad4..23201f75 100644
--- a/windows/alloc.cpp
+++ b/windows/alloc.cpp
@@ -45,6 +45,7 @@ void *uiRealloc(void *_p, size_t size, const char *type)
 	if (p == NULL)
 		return uiAlloc(size, type);
 	arr = heap[p];
+	// TODO does this fill in?
 	arr->resize(size, 0);
 	heap.erase(p);
 	heap[rawBytes(arr)] = arr;