diff --git a/Include/graminit.h b/Include/graminit.h
index 76da6a4165a..38b4dacff16 100644
--- a/Include/graminit.h
+++ b/Include/graminit.h
@@ -1,3 +1,5 @@
+/* Generated by Parser/pgen */
+
 #define single_input 256
 #define file_input 257
 #define eval_input 258
diff --git a/Parser/printgrammar.c b/Parser/printgrammar.c
index 55406981407..ec8f4daa4ef 100644
--- a/Parser/printgrammar.c
+++ b/Parser/printgrammar.c
@@ -13,6 +13,7 @@ static void printlabels(grammar *, FILE *);
 void
 printgrammar(grammar *g, FILE *fp)
 {
+	fprintf(fp, "/* Generated by Parser/pgen */\n\n");
 	fprintf(fp, "#include \"pgenheaders.h\"\n");
 	fprintf(fp, "#include \"grammar.h\"\n");
 	printdfas(g, fp);
@@ -31,6 +32,8 @@ printnonterminals(grammar *g, FILE *fp)
 	dfa *d;
 	int i;
 	
+	fprintf(fp, "/* Generated by Parser/pgen */\n\n");
+	
 	d = g->g_dfa;
 	for (i = g->g_ndfas; --i >= 0; d++)
 		fprintf(fp, "#define %s %d\n", d->d_name, d->d_type);
diff --git a/Python/graminit.c b/Python/graminit.c
index a0018265fd7..14a41d1b2ea 100644
--- a/Python/graminit.c
+++ b/Python/graminit.c
@@ -1,3 +1,5 @@
+/* Generated by Parser/pgen */
+
 #include "pgenheaders.h"
 #include "grammar.h"
 static arc arcs_0_0[3] = {