diff --git a/mlir/lib/Transforms/Utils/OneToNTypeConversion.cpp b/mlir/lib/Transforms/Utils/OneToNTypeConversion.cpp
--- a/mlir/lib/Transforms/Utils/OneToNTypeConversion.cpp
+++ b/mlir/lib/Transforms/Utils/OneToNTypeConversion.cpp
@@ -211,6 +211,8 @@
   // original op with those.
   assert(newValues.size() == resultMapping.getConvertedTypes().size());
   assert(op->getResultTypes() == resultMapping.getOriginalTypes());
+  PatternRewriter::InsertionGuard g(*this);
+  setInsertionPointAfter(op);
   SmallVector<Value> castResults =
       buildUnrealizedBackwardsCasts(newValues, resultMapping, *this);
   replaceOp(op, castResults);
@@ -218,6 +220,8 @@
 
 Block *OneToNPatternRewriter::applySignatureConversion(
     Block *block, OneToNTypeMapping &argumentConversion) {
+  PatternRewriter::InsertionGuard g(*this);
+
   // Split the block at the beginning to get a new block to use for the
   // updated signature.
   SmallVector<Location> locs;