diff --git a/paddle/gserver/gradientmachines/RecurrentGradientMachine.cpp b/paddle/gserver/gradientmachines/RecurrentGradientMachine.cpp
index bf7aa1c8d89aeff396a4ed094fc36043defeb1a5..bee82faa5fca8bb82848b862a239258a8165ce7b 100644
--- a/paddle/gserver/gradientmachines/RecurrentGradientMachine.cpp
+++ b/paddle/gserver/gradientmachines/RecurrentGradientMachine.cpp
@@ -676,7 +676,8 @@ void RecurrentGradientMachine::createInFrameInfo(int inlinkId,
   if (hasSubseq) {
     // inFrameLine create sequenceStartPositions one time
     CHECK_EQ(sequenceStartPositions.size(),
-             maxSequenceLength_ + input.getNumSubSequences());
+             static_cast<size_t>(maxSequenceLength_ +
+                                 input.getNumSubSequences()));
     CHECK_EQ(inlinkInfo->seqStartPosIndex.size(),
              static_cast<size_t>(maxSequenceLength_ + 1));
     createSeqPos(sequenceStartPositions, &inlinkInfo->sequenceStartPositions);