diff --git a/dlls/ws2_32/async.c b/dlls/ws2_32/async.c
index cc330bbd077..573349fe92e 100644
--- a/dlls/ws2_32/async.c
+++ b/dlls/ws2_32/async.c
@@ -384,7 +384,7 @@ HANDLE WINAPI WSAAsyncGetServByName(HWND hWnd, UINT uMsg, LPCSTR name,
 {
     struct async_query_getservbyname *aq;
     unsigned int len1 = strlen(name) + 1;
-    unsigned int len2 = strlen(proto) + 1;
+    unsigned int len2 = proto ? strlen(proto) + 1 : 0;
 
     TRACE("hwnd %p, msg %04x, name %s, proto %s\n", hWnd, uMsg, debugstr_a(name), debugstr_a(proto));
 
@@ -393,10 +393,18 @@ HANDLE WINAPI WSAAsyncGetServByName(HWND hWnd, UINT uMsg, LPCSTR name,
         SetLastError( WSAEWOULDBLOCK );
         return 0;
     }
+
     aq->serv_name  = (char *)(aq + 1);
-    aq->serv_proto = aq->serv_name + len1;
     strcpy( aq->serv_name, name );
-    strcpy( aq->serv_proto, proto );
+
+    if (proto)
+    {
+        aq->serv_proto = aq->serv_name + len1;
+        strcpy( aq->serv_proto, proto );
+    }
+    else
+        aq->serv_proto = NULL;
+
     return run_query( hWnd, uMsg, async_getservbyname, &aq->query, sbuf, buflen );
 }
 
diff --git a/dlls/ws2_32/tests/sock.c b/dlls/ws2_32/tests/sock.c
index 2de23c96471..f4cc909ec1e 100644
--- a/dlls/ws2_32/tests/sock.c
+++ b/dlls/ws2_32/tests/sock.c
@@ -5203,6 +5203,33 @@ static void test_WSAAsyncGetServByPort(void)
     DestroyWindow(hwnd);
 }
 
+static void test_WSAAsyncGetServByName(void)
+{
+    HWND hwnd = create_async_message_window();
+    HANDLE ret;
+    char buffer[MAXGETHOSTSTRUCT];
+
+    if (!hwnd)
+        return;
+
+    /* FIXME: The asynchronous window messages should be tested. */
+
+    /* Parameters are not checked when initiating the asynchronous operation.  */
+    ret = WSAAsyncGetServByName(hwnd, WM_ASYNCCOMPLETE, "", NULL, NULL, 0);
+    ok(ret != NULL, "WSAAsyncGetServByName returned NULL\n");
+
+    ret = WSAAsyncGetServByName(hwnd, WM_ASYNCCOMPLETE, "", "", buffer, MAXGETHOSTSTRUCT);
+    ok(ret != NULL, "WSAAsyncGetServByName returned NULL\n");
+
+    ret = WSAAsyncGetServByName(hwnd, WM_ASYNCCOMPLETE, "http", NULL, NULL, 0);
+    ok(ret != NULL, "WSAAsyncGetServByName returned NULL\n");
+
+    ret = WSAAsyncGetServByName(hwnd, WM_ASYNCCOMPLETE, "http", "tcp", buffer, MAXGETHOSTSTRUCT);
+    ok(ret != NULL, "WSAAsyncGetServByName returned NULL\n");
+
+    DestroyWindow(hwnd);
+}
+
 static void test_completion_port(void)
 {
     HANDLE previous_port, io_port;
@@ -5770,6 +5797,7 @@ START_TEST( sock )
     test_sioRoutingInterfaceQuery();
 
     test_WSAAsyncGetServByPort();
+    test_WSAAsyncGetServByName();
 
     test_completion_port();