diff --git a/src/lib/edid.c b/src/lib/edid.c
index fbd8ef65f5..957897ef52 100644
--- a/src/lib/edid.c
+++ b/src/lib/edid.c
@@ -175,12 +175,12 @@ detailed_cvt_descriptor(unsigned char *x, int first)
 static char *
 extract_string(unsigned char *x, int *valid_termination, int len)
 {
-	static char ret[128];
+	static char ret[EDID_ASCII_STRING_LENGTH + 1];
 	int i, seen_newline = 0;
 
 	memset(ret, 0, sizeof(ret));
 
-	for (i = 0; i < len; i++) {
+	for (i = 0; i < min(len, EDID_ASCII_STRING_LENGTH); i++) {
 		if (seen_newline) {
 			if (x[i] != 0x20) {
 				*valid_termination = 0;
@@ -285,7 +285,7 @@ detailed_block(struct edid *result_edid, unsigned char *x, int in_extension,
 			printk(BIOS_SPEW, "Monitor name: %s\n",
 			       extract_string(x + 5,
 					      &c->has_valid_string_termination,
-					      13));
+					      EDID_ASCII_STRING_LENGTH));
 			return 1;
 		case 0xFD:
 		{
@@ -477,7 +477,8 @@ detailed_block(struct edid *result_edid, unsigned char *x, int in_extension,
 		case 0xFF:
 			printk(BIOS_SPEW, "Serial number: %s\n",
 			       extract_string(x + 5,
-			       &c->has_valid_string_termination, 13));
+			       &c->has_valid_string_termination,
+			       EDID_ASCII_STRING_LENGTH));
 			return 1;
 		default:
 			printk(BIOS_SPEW,