diff --git a/dlls/ws2_32/socket.c b/dlls/ws2_32/socket.c
index 1bcff894620..932483325c8 100644
--- a/dlls/ws2_32/socket.c
+++ b/dlls/ws2_32/socket.c
@@ -4868,7 +4868,7 @@ INT WINAPI WSAAddressToStringW( LPSOCKADDR sockaddr, DWORD len,
     p = strchrW( buffer, ':' );
     if (!((SOCKADDR_IN *)sockaddr)->sin_port) *p = 0;
 
-    size = strlenW( buffer );
+    size = strlenW( buffer ) + 1;
 
     if (*lenstr <  size)
     {
@@ -4876,6 +4876,7 @@ INT WINAPI WSAAddressToStringW( LPSOCKADDR sockaddr, DWORD len,
         return SOCKET_ERROR;
     }
 
+    *lenstr = size;
     lstrcpyW( string, buffer );
     return 0;
 }
diff --git a/dlls/ws2_32/tests/sock.c b/dlls/ws2_32/tests/sock.c
index eb76a8651ea..cd88b8dd25d 100644
--- a/dlls/ws2_32/tests/sock.c
+++ b/dlls/ws2_32/tests/sock.c
@@ -1369,6 +1369,7 @@ static void test_WSAAddressToStringW(void)
     ok( !ret, "WSAAddressToStringW() failed unexpectedly: %d\n", WSAGetLastError() );
 
     ok( !lstrcmpW( address, expect1 ), "Expected different address string\n" );
+    ok( len == sizeof( expect1 )/sizeof( WCHAR ), "Expected size to be %d, got %d\n", sizeof( expect1 )/sizeof( WCHAR ), len);
 
     len = sizeof(address);
 
@@ -1402,6 +1403,7 @@ static void test_WSAAddressToStringW(void)
     ok( !ret, "WSAAddressToStringW() failed unexpectedly: %d\n", WSAGetLastError() );
 
     ok( !lstrcmpW( address, expect4 ), "Expected different address string\n" );
+    ok( len == sizeof( expect4 )/sizeof( WCHAR ), "Expected size to be %d, got %d\n", sizeof( expect4 )/sizeof( WCHAR ), len);
 }
 
 static void test_WSAStringToAddressA(void)