diff --git a/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp b/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp
index 328c605add65c..c6bcb593eaad8 100644
--- a/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp
+++ b/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp
@@ -295,7 +295,7 @@ static void restoreByValRefArgumentType(
         cast<TypeAttr>(byValRefAttr->getValue()).getValue());
 
     auto valueArg = rewriter.create<LLVM::LoadOp>(arg.getLoc(), resTy, arg);
-    rewriter.replaceUsesOfBlockArgument(oldArg, valueArg);
+    rewriter.replaceUsesOfBlockArgument(arg, valueArg);
   }
 }
 
diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
index c4b85ec4f67d6..3b669f51a615f 100644
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -1743,7 +1743,7 @@ void ConversionPatternRewriter::replaceUsesOfBlockArgument(BlockArgument from,
   });
   impl->appendRewrite<ReplaceBlockArgRewrite>(from.getOwner(), from,
                                               impl->currentTypeConverter);
-  impl->mapping.map(impl->mapping.lookupOrDefault(from), to);
+  impl->mapping.map(from, to);
 }
 
 Value ConversionPatternRewriter::getRemappedValue(Value key) {