diff --git a/lib/x509asn1.c b/lib/x509asn1.c
index c4bc7c1fd..bba20233f 100644
--- a/lib/x509asn1.c
+++ b/lib/x509asn1.c
@@ -466,6 +466,7 @@ static const char *GTime2str(const char *beg, const char *end)
     break;
   case 2:
     sec1 = fracp[-2];
+    /* FALLTHROUGH */
   case 1:
     sec2 = fracp[-1];
     break;