diff --git a/mlir/lib/Transforms/DialectConversion.cpp b/mlir/lib/Transforms/DialectConversion.cpp
index 3f202c2a95bc6..bf79266dc8b1d 100644
--- a/mlir/lib/Transforms/DialectConversion.cpp
+++ b/mlir/lib/Transforms/DialectConversion.cpp
@@ -783,7 +783,7 @@ void ConversionPatternRewriterImpl::notifyRegionIsBeingInlinedBefore(
     Region &region, Region &parent, Region::iterator before) {
   for (auto &pair : llvm::enumerate(region)) {
     Block &block = pair.value();
-    unsigned position = pair.index();
+    Region::iterator::difference_type position = pair.index();
     blockActions.push_back(BlockAction::getMove(&block, {&region, position}));
   }
 }