diff --git a/flang/lib/Lower/IO.cpp b/flang/lib/Lower/IO.cpp
index 68ef2f7822a68..fc95e1146ee39 100644
--- a/flang/lib/Lower/IO.cpp
+++ b/flang/lib/Lower/IO.cpp
@@ -420,8 +420,10 @@ static mlir::FuncOp getOutputFunc(mlir::Location loc,
       return getIORuntimeFunc<mkIOKey(OutputInteger32)>(loc, builder);
     case 64:
       return getIORuntimeFunc<mkIOKey(OutputInteger64)>(loc, builder);
+#ifdef __SIZEOF_INT128__
     case 128:
       return getIORuntimeFunc<mkIOKey(OutputInteger128)>(loc, builder);
+#endif
     }
     llvm_unreachable("unknown OutputInteger kind");
   }