make Python-ast.c depend on Python-ast.h
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 0a3df8d..07aa5bf 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -614,7 +614,7 @@
 $(AST_H): $(AST_ASDL) $(ASDLGEN_FILES)
 	$(ASDLGEN) -h $(AST_H_DIR) $(AST_ASDL)
 
-$(AST_C): $(AST_ASDL) $(ASDLGEN_FILES)
+$(AST_C): $(AST_H) $(AST_ASDL) $(ASDLGEN_FILES)
 	$(ASDLGEN) -c $(AST_C_DIR) $(AST_ASDL)
 
 Python/compile.o Python/symtable.o Python/ast.o: $(GRAMMAR_H) $(AST_H)