diff --git a/llvm/lib/CodeGenData/OutlinedHashTreeRecord.cpp b/llvm/lib/CodeGenData/OutlinedHashTreeRecord.cpp
index 996a57fd5e713..d3c6790408388 100644
--- a/llvm/lib/CodeGenData/OutlinedHashTreeRecord.cpp
+++ b/llvm/lib/CodeGenData/OutlinedHashTreeRecord.cpp
@@ -119,8 +119,8 @@ void OutlinedHashTreeRecord::convertToStableData(
       [&NodeIdMap](const HashNode *Current) {
         size_t Index = NodeIdMap.size();
         NodeIdMap[Current] = Index;
-        assert(Index = NodeIdMap.size() + 1 &&
-                       "Expected size of NodeMap to increment by 1");
+        assert((Index + 1 == NodeIdMap.size()) &&
+               "Duplicate key in NodeIdMap: 'Current' should be unique.");
       },
       /*EdgeCallbackFn=*/nullptr, /*SortedWork=*/true);