diff --git a/paddle/trainer/ThreadParameterUpdater.cpp b/paddle/trainer/ThreadParameterUpdater.cpp
index a26e9239f987f63ecbcf0183582ca64d64b50af6..d0fda1b6253e3e4b11a7e6b956d9a93ad5596728 100644
--- a/paddle/trainer/ThreadParameterUpdater.cpp
+++ b/paddle/trainer/ThreadParameterUpdater.cpp
@@ -258,7 +258,7 @@ void SgdThreadUpdater::threadUpdateSparse(
     }
     // For numThreads > 1, MultiGradientMachine is used, which goes
     // to the above branch.
-    CHECK_EQ(numThreads, 1);
+    CHECK_EQ(numThreads, 1UL);
     mainMat->clearIndices();
   } else {
     auto & m = *para->getMat(PARAMETER_GRADIENT).get();