diff --git a/src/bitops.c b/src/bitops.c
index 435ab7a33..5190e1035 100644
--- a/src/bitops.c
+++ b/src/bitops.c
@@ -508,7 +508,7 @@ robj *lookupStringForBitCommand(client *c, uint64_t maxbit, int *created) {
  * If the source object is NULL the function is guaranteed to return NULL
  * and set 'len' to 0. */
 unsigned char *getObjectReadOnlyString(robj *o, long *len, char *llbuf) {
-    serverAssert(o->type == OBJ_STRING);
+    serverAssert(!o || o->type == OBJ_STRING);
     unsigned char *p = NULL;
 
     /* Set the 'p' pointer to the string, that can be just a stack allocated