diff --git a/zirgen/Dialect/BigInt/Bytecode/decode.cpp b/zirgen/Dialect/BigInt/Bytecode/decode.cpp
index a5f9ccc9..c33f69d6 100644
--- a/zirgen/Dialect/BigInt/Bytecode/decode.cpp
+++ b/zirgen/Dialect/BigInt/Bytecode/decode.cpp
@@ -149,6 +149,8 @@ mlir::func::FuncOp decode(mlir::ModuleOp module, const Program& prog) {
     }
   }
 
+  // Add terminator op, for the sake of propriety.
+  builder.create<mlir::func::ReturnOp>(loc);
   return out;
 }
 
diff --git a/zirgen/Dialect/BigInt/IR/Eval.cpp b/zirgen/Dialect/BigInt/IR/Eval.cpp
index 0959e302..10b9d52d 100644
--- a/zirgen/Dialect/BigInt/IR/Eval.cpp
+++ b/zirgen/Dialect/BigInt/IR/Eval.cpp
@@ -188,7 +188,7 @@ EvalOutput eval(func::FuncOp inFunc, ArrayRef<APInt> witnessValues) {
 
   llvm::DenseMap<Value, BytePoly> polys;
 
-  for (Operation& origOp : inFunc.getBody().front()) {
+  for (Operation& origOp : inFunc.getBody().front().without_terminator()) {
     llvm::TypeSwitch<Operation*>(&origOp)
         .Case<DefOp>([&](auto op) {
           APInt val = witnessValues[op.getLabel()];