diff --git a/mlir/lib/Dialect/Shape/Transforms/ShapeTypeConversion.cpp b/mlir/lib/Dialect/Shape/Transforms/ShapeTypeConversion.cpp
--- a/mlir/lib/Dialect/Shape/Transforms/ShapeTypeConversion.cpp
+++ b/mlir/lib/Dialect/Shape/Transforms/ShapeTypeConversion.cpp
@@ -45,11 +45,9 @@
     auto newAssumingOp = rewriter.create<shape::AssumingOp>(
         assumingOp.getLoc(), newResultTypes, assumingOp.witness());
 
-    // Handle the region transfer carefully here to avoid assertions that both
-    // operations are valid at replacement time.
-    newAssumingOp.doRegion().push_back(new Block());
     rewriter.replaceOp(assumingOp, newAssumingOp.getResults());
-    newAssumingOp.doRegion().takeBody(assumingOp.doRegion());
+    rewriter.inlineRegionBefore(assumingOp.doRegion(), newAssumingOp.doRegion(),
+                                newAssumingOp.doRegion().end());
 
     return success();
   }