diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
index 1fdc6bc..60b53e9 100755
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -366,9 +366,9 @@
         self.emit("obj2ast_%s(PyObject* obj, %s* out, PyArena* arena)" % (name, ctype), 0)
         self.emit("{", 0)
         self.emit("PyObject* tmp = NULL;", 1)
+        self.emit("int isinstance;", 1)
         # Prevent compiler warnings about unused variable.
         self.emit("tmp = tmp;", 1)
-        self.emit("int isinstance;", 1)
         self.emit("", 0)
 
     def sumTrailer(self, name, add_label=False):