diff --git a/dlls/winhttp/request.c b/dlls/winhttp/request.c
index 38150ecce1f..2053c96c537 100644
--- a/dlls/winhttp/request.c
+++ b/dlls/winhttp/request.c
@@ -2443,7 +2443,7 @@ static HRESULT WINAPI winhttp_request_Open(
     TRACE("%p, %s, %s, %s\n", request, debugstr_w(method), debugstr_w(url),
           debugstr_variant(&async));
 
-    if (!method) return E_INVALIDARG;
+    if (!method || !url) return E_INVALIDARG;
 
     memset( &uc, 0, sizeof(uc) );
     uc.dwStructSize = sizeof(uc);
@@ -2667,6 +2667,7 @@ static HRESULT WINAPI winhttp_request_get_Status(
 
     TRACE("%p, %p\n", request, status);
 
+    if (!status) return E_INVALIDARG;
     if (request->state < REQUEST_STATE_SENT)
     {
         return HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND );
@@ -2692,6 +2693,7 @@ static HRESULT WINAPI winhttp_request_get_StatusText(
 
     TRACE("%p, %p\n", request, status);
 
+    if (!status) return E_INVALIDARG;
     if (request->state < REQUEST_STATE_SENT)
     {
         return HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND );
@@ -2808,6 +2810,11 @@ static HRESULT WINAPI winhttp_request_get_ResponseText(
 
     TRACE("%p, %p\n", request, body);
 
+    if (!body) return E_INVALIDARG;
+    if (request->state < REQUEST_STATE_SENT)
+    {
+        return HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND );
+    }
     if ((err = request_read_body( request, INFINITE ))) return HRESULT_FROM_WIN32( err );
     if ((err = request_get_codepage( request, &codepage ))) return HRESULT_FROM_WIN32( err );
 
@@ -2830,6 +2837,7 @@ static HRESULT WINAPI winhttp_request_get_ResponseBody(
 
     TRACE("%p, %p\n", request, body);
 
+    if (!body) return E_INVALIDARG;
     if ((err = request_read_body( request, INFINITE ))) return HRESULT_FROM_WIN32( err );
 
     if (!(sa = SafeArrayCreateVector( VT_UI1, 0, request->offset ))) return E_OUTOFMEMORY;
diff --git a/dlls/winhttp/tests/winhttp.c b/dlls/winhttp/tests/winhttp.c
index f70b554629e..e3f1fb6a6ba 100644
--- a/dlls/winhttp/tests/winhttp.c
+++ b/dlls/winhttp/tests/winhttp.c
@@ -2114,7 +2114,7 @@ static void test_IWinHttpRequest(void)
     static const WCHAR bypas_listW[] = {'b','y','p','a','s','s','l','i','s','t',0};
     HRESULT hr;
     IWinHttpRequest *req;
-    BSTR method, url, username, password, response = NULL, status_text = NULL;
+    BSTR method, url, username, password, response = NULL, status_text = NULL, headers = NULL;
     VARIANT async, empty, timeout, body, proxy_server, bypass_list;
     VARIANT_BOOL succeeded;
     LONG status;
@@ -2126,6 +2126,9 @@ static void test_IWinHttpRequest(void)
     VariantInit( &empty );
     V_VT( &empty ) = VT_ERROR;
 
+    V_VT( &async ) = VT_BOOL;
+    V_BOOL( &async ) = VARIANT_FALSE;
+
     hr = IWinHttpRequest_Open( req, NULL, NULL, empty );
     ok( hr == E_INVALIDARG, "got %08x\n", hr );
 
@@ -2133,6 +2136,9 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_Open( req, method, NULL, empty );
     ok( hr == E_INVALIDARG, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_Open( req, method, NULL, async );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     url = SysAllocString( url1W );
     hr = IWinHttpRequest_Open( req, NULL, url, empty );
     ok( hr == E_INVALIDARG, "got %08x\n", hr );
@@ -2152,10 +2158,6 @@ static void test_IWinHttpRequest(void)
     hr = CoCreateInstance( &CLSID_WinHttpRequest, NULL, CLSCTX_INPROC_SERVER, &IID_IWinHttpRequest, (void **)&req );
     ok( hr == S_OK, "got %08x\n", hr );
 
-    VariantInit( &async );
-    V_VT( &async ) = VT_BOOL;
-    V_BOOL( &async ) = VARIANT_FALSE;
-
     SysFreeString( url );
     url = SysAllocString( url2W );
     hr = IWinHttpRequest_Open( req, method, url, async );
@@ -2188,12 +2190,27 @@ static void test_IWinHttpRequest(void)
     hr = CoCreateInstance( &CLSID_WinHttpRequest, NULL, CLSCTX_INPROC_SERVER, &IID_IWinHttpRequest, (void **)&req );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
+    hr = IWinHttpRequest_get_ResponseText( req, &response );
+    ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
+
+    hr = IWinHttpRequest_get_Status( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_get_Status( req, &status );
     ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_StatusText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_get_StatusText( req, &status_text );
     ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseBody( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_SetTimeouts( req, 10000, 10000, 10000, 10000 );
     ok( hr == S_OK, "got %08x\n", hr );
 
@@ -2213,6 +2230,12 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_SetProxy( req, HTTPREQUEST_PROXYSETTING_DIRECT, proxy_server, bypass_list );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, &headers );
+    ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
+
     SysFreeString( method );
     method = SysAllocString( method1W );
     SysFreeString( url );
@@ -2220,12 +2243,21 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_Open( req, method, url, async );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
+    hr = IWinHttpRequest_get_ResponseText( req, &response );
+    ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
+
     hr = IWinHttpRequest_get_Status( req, &status );
     ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
 
     hr = IWinHttpRequest_get_StatusText( req, &status_text );
     ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseBody( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_SetTimeouts( req, 10000, 10000, 10000, 10000 );
     ok( hr == S_OK, "got %08x\n", hr );
 
@@ -2237,9 +2269,15 @@ static void test_IWinHttpRequest(void)
     ok( hr == E_INVALIDARG, "got %08x\n", hr );
 
     password = SysAllocString( passwordW );
+    hr = IWinHttpRequest_SetCredentials( req, NULL, password, 0xdeadbeef );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_SetCredentials( req, username, password, 0xdeadbeef );
     ok( hr == E_INVALIDARG, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_SetCredentials( req, NULL, password, HTTPREQUEST_SETCREDENTIALS_FOR_SERVER );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_SetCredentials( req, username, password, HTTPREQUEST_SETCREDENTIALS_FOR_SERVER );
     ok( hr == S_OK, "got %08x\n", hr );
 
@@ -2256,22 +2294,41 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_SetProxy( req, HTTPREQUEST_PROXYSETTING_DIRECT, proxy_server, bypass_list );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, &headers );
+    ok( hr == HRESULT_FROM_WIN32( ERROR_WINHTTP_CANNOT_CALL_BEFORE_SEND ), "got %08x\n", hr );
+
     hr = IWinHttpRequest_Send( req, empty );
     ok( hr == S_OK, "got %08x\n", hr );
 
     hr = IWinHttpRequest_Send( req, empty );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
+    hr = IWinHttpRequest_get_ResponseText( req, &response );
+    ok( hr == S_OK, "got %08x\n", hr );
+    SysFreeString( response );
+
+    hr = IWinHttpRequest_get_Status( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     status = 0;
     hr = IWinHttpRequest_get_Status( req, &status );
     ok( hr == S_OK, "got %08x\n", hr );
     trace("%d\n", status);
 
+    hr = IWinHttpRequest_get_StatusText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_get_StatusText( req, &status_text );
     ok( hr == S_OK, "got %08x\n", hr );
     trace("%s\n", wine_dbgstr_w(status_text));
     SysFreeString( status_text );
 
+    hr = IWinHttpRequest_get_ResponseBody( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_SetCredentials( req, username, password, HTTPREQUEST_SETCREDENTIALS_FOR_SERVER );
     ok( hr == S_OK, "got %08x\n", hr );
 
@@ -2281,6 +2338,13 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_SetProxy( req, HTTPREQUEST_PROXYSETTING_DIRECT, proxy_server, bypass_list );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, &headers );
+    ok( hr == S_OK, "got %08x\n", hr );
+    SysFreeString( headers );
+
     VariantInit( &timeout );
     V_VT( &timeout ) = VT_I4;
     V_I4( &timeout ) = 10;
@@ -2306,10 +2370,16 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_Send( req, empty );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_get_ResponseText( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     hr = IWinHttpRequest_get_ResponseText( req, &response );
     ok( hr == S_OK, "got %08x\n", hr );
     SysFreeString( response );
 
+    hr = IWinHttpRequest_get_ResponseBody( req, NULL );
+    ok( hr == E_INVALIDARG, "got %08x\n", hr );
+
     VariantInit( &body );
     V_VT( &body ) = VT_ERROR;
     hr = IWinHttpRequest_get_ResponseBody( req, &body );
@@ -2325,6 +2395,10 @@ static void test_IWinHttpRequest(void)
     hr = IWinHttpRequest_SetProxy( req, HTTPREQUEST_PROXYSETTING_DIRECT, proxy_server, bypass_list );
     ok( hr == S_OK, "got %08x\n", hr );
 
+    hr = IWinHttpRequest_GetAllResponseHeaders( req, &headers );
+    ok( hr == S_OK, "got %08x\n", hr );
+    SysFreeString( headers );
+
     hr = IWinHttpRequest_Send( req, empty );
     ok( hr == S_OK, "got %08x\n", hr );