diff --git a/NEWS b/NEWS
index ea08065ce01..3cf7c303fcc 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,8 @@ PHP                                                                        NEWS
   . Extended --ini to print INI settings changed from the builtin default.
     (timwolla)
   . Drop support for -z CLI/CGI flag. (nielsdos)
+  . Fixed GH-17956 - development server 404 page does not adapt to mobiles.
+    (pascalchevrel)
 
 - COM:
   . Fixed property access of PHP objects wrapped in variant. (cmb)
diff --git a/sapi/cli/php_cli_server.c b/sapi/cli/php_cli_server.c
index 9e8d8d1b8a4..b7e3e5fa1be 100644
--- a/sapi/cli/php_cli_server.c
+++ b/sapi/cli/php_cli_server.c
@@ -2026,7 +2026,7 @@ static zend_result php_cli_server_send_error_page(php_cli_server *server, php_cl
 		escaped_request_uri = php_escape_html_entities_ex((const unsigned char *) ZSTR_VAL(client->request.request_uri), ZSTR_LEN(client->request.request_uri), 0, ENT_QUOTES, NULL, /* double_encode */ 0, /* quiet */ 0);
 
 		{
-			static const char prologue_template[] = "<!doctype html><html><head><title>%d %s</title>";
+			static const char prologue_template[] = "<!doctype html><html><head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\"><title>%d %s</title>";
 			php_cli_server_chunk *chunk = php_cli_server_chunk_heap_new_self_contained(strlen(prologue_template) + 3 + strlen(status_string) + 1);
 			if (!chunk) {
 				goto fail;
diff --git a/sapi/cli/tests/php_cli_server_013.phpt b/sapi/cli/tests/php_cli_server_013.phpt
index fb334206908..ab898a402f9 100644
--- a/sapi/cli/tests/php_cli_server_013.phpt
+++ b/sapi/cli/tests/php_cli_server_013.phpt
@@ -131,7 +131,7 @@ X-Powered-By: PHP/%s
 Content-Type: text/html; charset=UTF-8
 Content-Length: %d
 
-<!doctype html><html><head><title>404 Not Found</title><style>AAA</style>
+<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>404 Not Found</title><style>AAA</style>
 </head><body><h1>Not Found</h1><p>The requested resource <code class="url">/</code> was not found on this server.</p></body></html>
 HTTP/1.1 404 Not Found
 Host: %s
@@ -141,7 +141,7 @@ X-Powered-By: PHP/%s
 Content-Type: text/html; charset=UTF-8
 Content-Length: %d
 
-<!doctype html><html><head><title>404 Not Found</title><style>AAA</style>
+<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>404 Not Found</title><style>AAA</style>
 </head><body><h1>Not Found</h1><p>The requested resource <code class="url">/main/style.css</code> was not found on this server.</p></body></html>
 HTTP/1.1 404 Not Found
 Host: %s
@@ -161,7 +161,7 @@ Content-Type: text/html; charset=UTF-8
 Content-Length: %d
 Allow: GET, HEAD, POST
 
-<!doctype html><html><head><title>405 Method Not Allowed</title><style>AAA</style>
+<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>405 Method Not Allowed</title><style>AAA</style>
 </head><body><h1>Method Not Allowed</h1><p>Requested method not allowed.</p></body></html>
 HTTP/1.1 405 Method Not Allowed
 Host: %s
@@ -172,7 +172,7 @@ Content-Type: text/html; charset=UTF-8
 Content-Length: %d
 Allow: GET, HEAD, POST
 
-<!doctype html><html><head><title>405 Method Not Allowed</title><style>AAA</style>
+<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>405 Method Not Allowed</title><style>AAA</style>
 </head><body><h1>Method Not Allowed</h1><p>Requested method not allowed.</p></body></html>
 HTTP/1.1 405 Method Not Allowed
 Host: %s
@@ -183,5 +183,5 @@ Content-Type: text/html; charset=UTF-8
 Content-Length: %d
 Allow: GET, HEAD, POST
 
-<!doctype html><html><head><title>405 Method Not Allowed</title><style>AAA</style>
+<!doctype html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><title>405 Method Not Allowed</title><style>AAA</style>
 </head><body><h1>Method Not Allowed</h1><p>Requested method not allowed.</p></body></html>
