diff --git a/lib/telnet.c b/lib/telnet.c
index 720fbd10ae..dc39de481c 100644
--- a/lib/telnet.c
+++ b/lib/telnet.c
@@ -844,10 +844,10 @@ static CURLcode check_telnet_options(struct Curl_easy *data)
           char *p;
           unsigned long x = strtoul(arg, &p, 10);
           unsigned long y = 0;
-          if(Curl_raw_tolower(*p) == 'x') {
+          if(x && (x <= 0xffff) && Curl_raw_tolower(*p) == 'x') {
             p++;
             y = strtoul(p, NULL, 10);
-            if(x && y && (x <= 0xffff) && (y <= 0xffff)) {
+            if(y && (y <= 0xffff)) {
               tn->subopt_wsx = (unsigned short)x;
               tn->subopt_wsy = (unsigned short)y;
               tn->us_preferred[CURL_TELOPT_NAWS] = CURL_YES;