diff --git a/src/hyperloglog.c b/src/hyperloglog.c
index ddbcf9bfd1d2789ab0596331fed4fff7b0946fa7..7fad34d5bb5d9d4ae642a27aa717e50270b65508 100644
--- a/src/hyperloglog.c
+++ b/src/hyperloglog.c
@@ -541,6 +541,9 @@ void pfcountCommand(redisClient *c) {
             card |= (uint64_t)registers[REDIS_HLL_SIZE-9] << 56;
         } else {
             /* Recompute it and update the cached value. */
+            o = dbUnshareStringValue(c->db,c->argv[1],o);
+            registers = o->ptr;
+
             card = hllCount(registers);
             registers[REDIS_HLL_SIZE-16] = card & 0xff;
             registers[REDIS_HLL_SIZE-15] = (card >> 8) & 0xff;