diff --git a/dlls/wininet/cookie.c b/dlls/wininet/cookie.c
index 46adf68bb26..5253b2b9586 100644
--- a/dlls/wininet/cookie.c
+++ b/dlls/wininet/cookie.c
@@ -678,6 +678,43 @@ BOOL WINAPI InternetGetCookieA(LPCSTR lpszUrl, LPCSTR lpszCookieName,
     return r;
 }
 
+
+/***********************************************************************
+ *           IsDomainLegalCookieDomainW (WININET.@)
+ */
+BOOL WINAPI IsDomainLegalCookieDomainW( LPCWSTR s1, LPCWSTR s2 )
+{
+    DWORD s1_len, s2_len;
+
+    FIXME("(%s, %s) semi-stub\n", debugstr_w(s1), debugstr_w(s2));
+
+    if (!s1 || !s2)
+    {
+        SetLastError(ERROR_INVALID_PARAMETER);
+        return FALSE;
+    }
+    if (s1[0] == '.' || !s1[0] || s2[0] == '.' || !s2[0])
+    {
+        SetLastError(ERROR_INVALID_NAME);
+        return FALSE;
+    }
+    if(!strchrW(s1, '.') || !strchrW(s2, '.'))
+        return FALSE;
+
+    s1_len = strlenW(s1);
+    s2_len = strlenW(s2);
+    if (s1_len > s2_len)
+        return FALSE;
+
+    if (strncmpiW(s1, s2+s2_len-s1_len, s1_len) || (s2_len>s1_len && s2[s2_len-s1_len-1]!='.'))
+    {
+        SetLastError(ERROR_INVALID_PARAMETER);
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
 BOOL set_cookie(LPCWSTR domain, LPCWSTR path, LPCWSTR cookie_name, LPCWSTR cookie_data)
 {
     cookie_domain *thisCookieDomain = NULL;
@@ -727,7 +764,26 @@ BOOL set_cookie(LPCWSTR domain, LPCWSTR path, LPCWSTR cookie_name, LPCWSTR cooki
 
         if (strncmpiW(ptr, szDomain, 7) == 0)
         {
-            ptr+=strlenW(szDomain);
+            WCHAR *end_ptr;
+
+            ptr += sizeof(szDomain)/sizeof(szDomain[0])-1;
+            if(*ptr == '.')
+                ptr++;
+            end_ptr = strchrW(ptr, ';');
+            if(end_ptr)
+                *end_ptr = 0;
+
+            if(!IsDomainLegalCookieDomainW(ptr, domain))
+            {
+                if(value != data)
+                    heap_free(value);
+                heap_free(data);
+                return FALSE;
+            }
+
+            if(end_ptr)
+                *end_ptr = ';';
+
             domain = ptr;
             TRACE("Parsing new domain %s\n",debugstr_w(domain));
         }
@@ -1059,28 +1115,3 @@ BOOL WINAPI InternetSetPerSiteCookieDecisionW( LPCWSTR pchHostName, DWORD dwDeci
     FIXME("(%s, 0x%08x) stub\n", debugstr_w(pchHostName), dwDecision);
     return FALSE;
 }
-
-/***********************************************************************
- *           IsDomainLegalCookieDomainW (WININET.@)
- */
-BOOL WINAPI IsDomainLegalCookieDomainW( LPCWSTR s1, LPCWSTR s2 )
-{
-    const WCHAR *p;
-
-    FIXME("(%s, %s)\n", debugstr_w(s1), debugstr_w(s2));
-
-    if (!s1 || !s2)
-    {
-        SetLastError(ERROR_INVALID_PARAMETER);
-        return FALSE;
-    }
-    if (s1[0] == '.' || !s1[0] || s2[0] == '.' || !s2[0])
-    {
-        SetLastError(ERROR_INVALID_NAME);
-        return FALSE;
-    }
-    if (!(p = strchrW(s2, '.'))) return FALSE;
-    if (strchrW(p + 1, '.') && !strcmpW(p + 1, s1)) return TRUE;
-    else if (!strcmpW(s1, s2)) return TRUE;
-    return FALSE;
-}
diff --git a/dlls/wininet/tests/internet.c b/dlls/wininet/tests/internet.c
index 5a8ba99153b..cf1fc4ed88e 100644
--- a/dlls/wininet/tests/internet.c
+++ b/dlls/wininet/tests/internet.c
@@ -496,6 +496,15 @@ static void test_complicated_cookie(void)
   ret = GetUrlCacheEntryInfo(buffer, NULL, &len);
   ok(!ret, "GetUrlCacheEntryInfo succeeded\n");
   ok(GetLastError() == ERROR_FILE_NOT_FOUND, "GetLastError() = %d\n", GetLastError());
+
+  /* try setting cookie for different domain */
+  ret = InternetSetCookie("http://www.aaa.example.com/bar",NULL,"E=F; domain=different.com");
+  ok(!ret, "InternetSetCookie succeeded\n");
+  ok(GetLastError() == ERROR_INVALID_PARAMETER, "GetLastError() = %d\n", GetLastError());
+  ret = InternetSetCookie("http://www.aaa.example.com.pl/bar",NULL,"E=F; domain=example.com.pl");
+  ok(ret, "InternetSetCookie failed with error: %d\n", GetLastError());
+  ret = InternetSetCookie("http://www.aaa.example.com.pl/bar",NULL,"E=F; domain=com.pl");
+  todo_wine ok(!ret, "InternetSetCookie succeeded\n");
 }
 
 static void test_cookie_url(void)
@@ -828,6 +837,8 @@ static void test_IsDomainLegalCookieDomainW(void)
     static const WCHAR dot_com[]        = {'.','c','o','m',0};
     static const WCHAR gmail_com[]      = {'g','m','a','i','l','.','c','o','m',0};
     static const WCHAR dot_gmail_com[]  = {'.','g','m','a','i','l','.','c','o','m',0};
+    static const WCHAR www_gmail_com[]  = {'w','w','w','.','g','m','a','i','l','.','c','o','m',0};
+    static const WCHAR www_mail_gmail_com[] = {'w','w','w','.','m','a','i','l','.','g','m','a','i','l','.','c','o','m',0};
     static const WCHAR mail_gmail_com[] = {'m','a','i','l','.','g','m','a','i','l','.','c','o','m',0};
     static const WCHAR gmail_co_uk[]    = {'g','m','a','i','l','.','c','o','.','u','k',0};
     static const WCHAR co_uk[]          = {'c','o','.','u','k',0};
@@ -924,6 +935,12 @@ static void test_IsDomainLegalCookieDomainW(void)
     ret = pIsDomainLegalCookieDomainW(gmail_com, gmail_com);
     ok(ret, "IsDomainLegalCookieDomainW failed\n");
 
+    ret = pIsDomainLegalCookieDomainW(gmail_com, www_gmail_com);
+    ok(ret, "IsDomainLegalCookieDomainW failed\n");
+
+    ret = pIsDomainLegalCookieDomainW(gmail_com, www_mail_gmail_com);
+    ok(ret, "IsDomainLegalCookieDomainW failed\n");
+
     SetLastError(0xdeadbeef);
     ret = pIsDomainLegalCookieDomainW(gmail_co_uk, co_uk);
     error = GetLastError();
@@ -940,6 +957,9 @@ static void test_IsDomainLegalCookieDomainW(void)
     ret = pIsDomainLegalCookieDomainW(gmail_co_uk, dot_co_uk);
     ok(!ret, "IsDomainLegalCookieDomainW succeeded\n");
 
+    ret = pIsDomainLegalCookieDomainW(co_uk, gmail_co_uk);
+    todo_wine ok(!ret, "IsDomainLegalCookieDomainW succeeded\n");
+
     ret = pIsDomainLegalCookieDomainW(gmail_co_uk, gmail_co_uk);
     ok(ret, "IsDomainLegalCookieDomainW failed\n");