diff --git a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
index aa5eb95a3d22ed..641b7d7e2d13be 100644
--- a/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
+++ b/mlir/lib/Dialect/Arith/IR/ArithOps.cpp
@@ -1739,6 +1739,8 @@ OpFoldResult arith::BitcastOp::fold(FoldAdaptor adaptor) {
   APInt bits = llvm::isa<FloatAttr>(operand)
                    ? llvm::cast<FloatAttr>(operand).getValue().bitcastToAPInt()
                    : llvm::cast<IntegerAttr>(operand).getValue();
+  assert(resType.getIntOrFloatBitWidth() == bits.getBitWidth() &&
+         "trying to fold on broken IR: operands have incompatible types");
 
   if (auto resFloatType = llvm::dyn_cast<FloatType>(resType))
     return FloatAttr::get(resType,