diff --git a/lib/altsvc.c b/lib/altsvc.c
index 108f5c0915..cf6f754a04 100644
--- a/lib/altsvc.c
+++ b/lib/altsvc.c
@@ -39,7 +39,7 @@
 #include "connect.h"
 
 #define MAX_ALTSVC_LINE    4095
-#define MAX_ALTSVC_DATELEN 256
+#define MAX_ALTSVC_DATELEN 17
 #define MAX_ALTSVC_HOSTLEN 2048
 #define MAX_ALTSVC_ALPNLEN 10
 
diff --git a/tests/data/test355 b/tests/data/test355
index 8cb29d3792..5c74321ac2 100644
--- a/tests/data/test355
+++ b/tests/data/test355
@@ -25,18 +25,22 @@ Funny-head: yesyes
 <client>
 <features>
 alt-svc
+Debug
 </features>
+<setenv>
+CURL_ALTSVC_HTTP=1
+</setenv>
 <server>
 http
 </server>
 <name>
-load Alt-Svc from file and use
+Alt-Svc from file with too long date
 </name>
 <command>
-http://%HOSTIP:%HTTPPORT/%TESTNUMBER --alt-svc ""
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER --alt-svc "%LOGDIR/altsvc-%TESTNUMBER"
 </command>
 <file name="%LOGDIR/altsvc-%TESTNUMBER">
-h1 example.com 80 h1 %HOSTIP %HTTPPORT "20290222 22:19:28" 0 0
+h1 %HOSTIP %HTTPPORT h1 example.com 80 "20290222 22:19:028" 0 0
 </file>
 </client>