diff --git a/lib/cpp/src/thrift/protocol/TDenseProtocol.cpp b/lib/cpp/src/thrift/protocol/TDenseProtocol.cpp
index d6644b7..583b630 100644
--- a/lib/cpp/src/thrift/protocol/TDenseProtocol.cpp
+++ b/lib/cpp/src/thrift/protocol/TDenseProtocol.cpp
@@ -155,7 +155,7 @@
   // If this is the end of the top-level write, we should have just popped
   // the TypeSpec passed to the constructor.
   if (ts_stack_.empty()) {
-    assert(old_tts = type_spec_);
+    assert(old_tts == type_spec_);
     return;
   }