diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
--- a/Parser/asdl_c.py
+++ b/Parser/asdl_c.py
@@ -1255,7 +1255,7 @@
         sys.exit(1)
     if INC_DIR:
         p = "%s/%s-ast.h" % (INC_DIR, mod.name)
-        f = open(p, "w")
+        f = open(p + ".tmp", "w")
         f.write(auto_gen_msg)
         f.write('#include "asdl.h"\n\n')
         c = ChainOfVisitors(TypeDefVisitor(f),
@@ -1267,10 +1267,11 @@
         f.write("mod_ty PyAST_obj2mod(PyObject* ast, PyArena* arena, int mode);\n")
         f.write("int PyAST_Check(PyObject* obj);\n")
         f.close()
+        os.rename(p + ".tmp", p)
 
     if SRC_DIR:
         p = os.path.join(SRC_DIR, str(mod.name) + "-ast.c")
-        f = open(p, "w")
+        f = open(p + ".tmp", "w")
         f.write(auto_gen_msg)
         f.write('#include <stddef.h>\n')
         f.write('\n')
@@ -1290,6 +1291,7 @@
             )
         v.visit(mod)
         f.close()
+        os.rename(p + ".tmp", p)
 
 if __name__ == "__main__":
     import sys