diff --git a/cper-utils.c b/cper-utils.c
index 1c2fb4b..c0f5b51 100644
--- a/cper-utils.c
+++ b/cper-utils.c
@@ -276,7 +276,7 @@
 //Helper function to convert an EDK EFI GUID into a string for intermediate use.
 void guid_to_string(char *out, EFI_GUID *guid)
 {
-	sprintf(out, "%08x-%04x-%04x-%02x%02x%02x%02x%02x%02x%02x%02x",
+	sprintf(out, "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
 		guid->Data1, guid->Data2, guid->Data3, guid->Data4[0],
 		guid->Data4[1], guid->Data4[2], guid->Data4[3], guid->Data4[4],
 		guid->Data4[5], guid->Data4[6], guid->Data4[7]);
@@ -291,7 +291,7 @@
 	}
 
 	sscanf(guid,
-	       "%08x-%04hx-%04hx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",
+	       "%08x-%04hx-%04hx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",
 	       &out->Data1, &out->Data2, &out->Data3, out->Data4,
 	       out->Data4 + 1, out->Data4 + 2, out->Data4 + 3, out->Data4 + 4,
 	       out->Data4 + 5, out->Data4 + 6, out->Data4 + 7);