diff --git a/src/libstrongswan/eap/eap.c b/src/libstrongswan/eap/eap.c
index 64b5dbe51..2b7295e3d 100644
--- a/src/libstrongswan/eap/eap.c
+++ b/src/libstrongswan/eap/eap.c
@@ -157,6 +157,7 @@ eap_vendor_type_t *eap_vendor_type_from_string(char *str)
 			type = eap_type_from_string(part);
 			if (!type)
 			{
+				errno = 0;
 				type = strtoul(part, &end, 0);
 				if (*end != '\0' || errno)
 				{
@@ -166,6 +167,7 @@ eap_vendor_type_t *eap_vendor_type_from_string(char *str)
 			}
 			continue;
 		}
+		errno = 0;
 		vendor = strtoul(part, &end, 0);
 		if (*end != '\0' || errno)
 		{