diff --git a/src/tracking.c b/src/tracking.c
index eb4113131..8c2dca7ba 100644
--- a/src/tracking.c
+++ b/src/tracking.c
@@ -102,7 +102,7 @@ void disableTracking(client *c) {
 /* Set the client 'c' to track the prefix 'prefix'. If the client 'c' is
  * already registered for the specified prefix, no operation is performed. */
 void enableBcastTrackingForPrefix(client *c, char *prefix, size_t plen) {
-    bcastState *bs = raxFind(PrefixTable,(unsigned char*)prefix,sdslen(prefix));
+    bcastState *bs = raxFind(PrefixTable,(unsigned char*)prefix,plen);
     /* If this is the first client subscribing to such prefix, create
      * the prefix in the table. */
     if (bs == raxNotFound) {