diff --git a/pandas/_libs/join.pyx b/pandas/_libs/join.pyx
index cc7d863bf326c..e574aa10f6b57 100644
--- a/pandas/_libs/join.pyx
+++ b/pandas/_libs/join.pyx
@@ -298,7 +298,7 @@ def left_join_indexer_unique(
             indexer[i] = j
             i += 1
 
-        if left[i] == right[j]:
+        if left[i] == rval:
             indexer[i] = j
             i += 1
             while i < nleft - 1 and left[i] == rval: