diff --git a/dlls/urlmon/tests/protocol.c b/dlls/urlmon/tests/protocol.c
index 25f78d0b71c..33585066c3c 100644
--- a/dlls/urlmon/tests/protocol.c
+++ b/dlls/urlmon/tests/protocol.c
@@ -197,18 +197,6 @@ static const WCHAR binding_urls[][130] = {
 
 static const CHAR post_data[] = "mode=Test";
 
-static const char *debugstr_guid(REFIID riid)
-{
-    static char buf[50];
-
-    sprintf(buf, "{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}",
-            riid->Data1, riid->Data2, riid->Data3, riid->Data4[0],
-            riid->Data4[1], riid->Data4[2], riid->Data4[3], riid->Data4[4],
-            riid->Data4[5], riid->Data4[6], riid->Data4[7]);
-
-    return buf;
-}
-
 static int strcmp_wa(LPCWSTR strw, const char *stra)
 {
     CHAR buf[512];
@@ -427,7 +415,7 @@ static HRESULT WINAPI ServiceProvider_QueryService(IServiceProvider *iface, REFG
         return E_NOINTERFACE;
     }
 
-    ok(0, "unexpected service %s\n", debugstr_guid(guidService));
+    ok(0, "unexpected service %s\n", wine_dbgstr_guid(guidService));
     return E_FAIL;
 }
 
@@ -1268,7 +1256,7 @@ static HRESULT QueryInterface(REFIID riid, void **ppv)
     if(*ppv)
         return S_OK;
 
-    ok(0, "unexpected call %s\n", debugstr_guid(riid));
+    ok(0, "unexpected call %s\n", wine_dbgstr_guid(riid));
     return E_NOINTERFACE;
 }
 
@@ -1532,7 +1520,7 @@ static HRESULT WINAPI ProtocolEmul_QueryInterface(IInternetProtocolEx *iface, RE
     }
 
     if(!IsEqualGUID(riid, &unknown_iid)) /* IE10 */
-        ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+        ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     *ppv = NULL;
     return E_NOINTERFACE;
 }
@@ -2064,7 +2052,7 @@ static HRESULT WINAPI MimeProtocol_QueryInterface(IInternetProtocolEx *iface, RE
         return S_OK;
     }
 
-    ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+    ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     *ppv = NULL;
     return E_NOINTERFACE;
 }
@@ -2275,7 +2263,7 @@ static HRESULT WINAPI ClassFactory_CreateInstance(IClassFactory *iface, IUnknown
     CHECK_EXPECT(CreateInstance);
 
     ok(pOuter == (IUnknown*)prot_bind_info, "pOuter != protocol_unk\n");
-    ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", debugstr_guid(riid));
+    ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", wine_dbgstr_guid(riid));
     ok(ppv != NULL, "ppv == NULL\n");
 
     *ppv = &Protocol;
@@ -2303,7 +2291,7 @@ static HRESULT WINAPI MimeFilter_CreateInstance(IClassFactory *iface, IUnknown *
     CHECK_EXPECT(MimeFilter_CreateInstance);
 
     ok(!outer, "outer = %p\n", outer);
-    ok(IsEqualGUID(&IID_IInternetProtocol, riid), "unexpected riid %s\n", debugstr_guid(riid));
+    ok(IsEqualGUID(&IID_IInternetProtocol, riid), "unexpected riid %s\n", wine_dbgstr_guid(riid));
 
     *ppv = &MimeProtocol;
     return S_OK;
diff --git a/dlls/urlmon/tests/url.c b/dlls/urlmon/tests/url.c
index 83c5c8d3c95..191e1782422 100644
--- a/dlls/urlmon/tests/url.c
+++ b/dlls/urlmon/tests/url.c
@@ -211,18 +211,6 @@ static enum {
     END_DOWNLOAD
 } download_state;
 
-static const char *debugstr_guid(REFIID riid)
-{
-    static char buf[50];
-
-    sprintf(buf, "{%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X}",
-            riid->Data1, riid->Data2, riid->Data3, riid->Data4[0],
-            riid->Data4[1], riid->Data4[2], riid->Data4[3], riid->Data4[4],
-            riid->Data4[5], riid->Data4[6], riid->Data4[7]);
-
-    return buf;
-}
-
 static BOOL proxy_active(void)
 {
     HKEY internet_settings;
@@ -397,11 +385,11 @@ static HRESULT WINAPI Protocol_QueryInterface(IInternetProtocol *iface, REFIID r
         return E_NOINTERFACE; /* TODO */
 
     if(IsEqualGUID(&IID_undocumentedIE10, riid)) {
-        trace("QI(%s)\n", debugstr_guid(riid));
+        trace("QI(%s)\n", wine_dbgstr_guid(riid));
         return E_NOINTERFACE; /* TODO */
     }
 
-    ok(0, "unexpected call %s\n", debugstr_guid(riid));
+    ok(0, "unexpected call %s\n", wine_dbgstr_guid(riid));
     return E_NOINTERFACE;
 }
 
@@ -1363,7 +1351,7 @@ static HRESULT WINAPI HttpSecurity_GetWindow(IHttpSecurity *iface, REFGUID rguid
     else if(IsEqualGUID(rguidReason, &IID_ICodeInstall))
         CHECK_EXPECT(GetWindow_ICodeInstall);
     else
-        ok(0, "Unexpected rguidReason: %s\n", debugstr_guid(rguidReason));
+        ok(0, "Unexpected rguidReason: %s\n", wine_dbgstr_guid(rguidReason));
 
     *phwnd = NULL;
     return S_OK;
@@ -1448,7 +1436,7 @@ static HRESULT WINAPI ServiceProvider_QueryService(IServiceProvider *iface,
         return E_NOINTERFACE;
     }
 
-    ok(0, "unexpected service %s\n", debugstr_guid(guidService));
+    ok(0, "unexpected service %s\n", wine_dbgstr_guid(guidService));
     return E_NOINTERFACE;
 }
 
@@ -1570,7 +1558,7 @@ static HRESULT WINAPI statusclb_QueryInterface(IBindStatusCallbackEx *iface, REF
         *ppv = NULL;
         return E_NOINTERFACE;
     }else {
-        ok(0, "unexpected interface %s\n", debugstr_guid(riid));
+        ok(0, "unexpected interface %s\n", wine_dbgstr_guid(riid));
     }
 
     return E_NOINTERFACE;
@@ -1632,7 +1620,7 @@ static HRESULT WINAPI statusclb_OnStartBinding(IBindStatusCallbackEx *iface, DWO
 
     hres = IBinding_GetBindResult(pib, &clsid, &res, &res_str, NULL);
     ok(hres == S_OK, "GetBindResult failed: %08x, expected S_OK\n", hres);
-    ok(IsEqualCLSID(&clsid, &CLSID_NULL), "incorrect clsid: %s\n", debugstr_guid(&clsid));
+    ok(IsEqualCLSID(&clsid, &CLSID_NULL), "incorrect clsid: %s\n", wine_dbgstr_guid(&clsid));
     ok(!res, "incorrect res: %x\n", res);
     ok(!res_str, "incorrect res_str: %s\n", wine_dbgstr_w(res_str));
 
@@ -1802,7 +1790,7 @@ static HRESULT WINAPI statusclb_OnProgress(IBindStatusCallbackEx *iface, ULONG u
         hr = CLSIDFromString((LPCOLESTR)szStatusText, &clsid);
         ok(hr == S_OK, "CLSIDFromString failed with error 0x%08x\n", hr);
         ok(IsEqualCLSID(&clsid, &CLSID_HTMLDocument),
-            "Expected clsid to be CLSID_HTMLDocument instead of %s\n", debugstr_guid(&clsid));
+            "Expected clsid to be CLSID_HTMLDocument instead of %s\n", wine_dbgstr_guid(&clsid));
         break;
     }
     case BINDSTATUS_BEGINSYNCOPERATION:
@@ -1894,31 +1882,31 @@ static HRESULT WINAPI statusclb_OnStopBinding(IBindStatusCallbackEx *iface, HRES
         if(hresult==S_OK || (abort_start && hresult!=S_FALSE) || hresult == REGDB_E_CLASSNOTREG) {
             ok(IsEqualCLSID(&clsid, &CLSID_NULL),
                     "incorrect protocol CLSID: %s, expected CLSID_NULL\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(emulate_protocol) {
             todo_wine ok(IsEqualCLSID(&clsid, &CLSID_FtpProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_FtpProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(test_protocol == FTP_TEST) {
             ok(IsEqualCLSID(&clsid, &CLSID_FtpProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_FtpProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(test_protocol == FILE_TEST) {
             ok(IsEqualCLSID(&clsid, &CLSID_FileProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_FileProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(test_protocol == HTTP_TEST) {
             ok(IsEqualCLSID(&clsid, &CLSID_HttpProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_HttpProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(test_protocol == HTTPS_TEST) {
             ok(IsEqualCLSID(&clsid, &CLSID_HttpSProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_HttpSProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else if(test_protocol == ABOUT_TEST) {
             ok(IsEqualCLSID(&clsid, &CLSID_AboutProtocol),
                     "incorrect protocol CLSID: %s, expected CLSID_AboutProtocol\n",
-                    debugstr_guid(&clsid));
+                    wine_dbgstr_guid(&clsid));
         }else {
             ok(0, "unexpected (%d)\n", test_protocol);
         }
@@ -2073,7 +2061,7 @@ static HRESULT WINAPI statusclb_OnObjectAvailable(IBindStatusCallbackEx *iface,
     if(iface != &objbsc)
         ok(0, "unexpected call\n");
 
-    ok(IsEqualGUID(&IID_IUnknown, riid), "riid = %s\n", debugstr_guid(riid));
+    ok(IsEqualGUID(&IID_IUnknown, riid), "riid = %s\n", wine_dbgstr_guid(riid));
     ok(punk != NULL, "punk == NULL\n");
 
     return S_OK;
@@ -2114,7 +2102,7 @@ static IBindStatusCallbackEx objbsc = { &BindStatusCallbackVtbl };
 static HRESULT WINAPI MonikerProp_QueryInterface(IMonikerProp *iface, REFIID riid, void **ppv)
 {
     *ppv = NULL;
-    ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+    ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     return E_NOINTERFACE;
 }
 
@@ -2166,7 +2154,7 @@ static HRESULT WINAPI PersistMoniker_QueryInterface(IPersistMoniker *iface, REFI
     if(*ppv)
         return S_OK;
 
-    ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+    ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     return E_NOINTERFACE;
 }
 
@@ -2314,7 +2302,7 @@ static HRESULT WINAPI ClassFactory_QueryInterface(IClassFactory *iface, REFIID r
     if(IsEqualGUID(&CLSID_IdentityUnmarshal, riid))
         return E_NOINTERFACE;
 
-    ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+    ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     return E_NOTIMPL;
 }
 
@@ -2332,7 +2320,7 @@ static HRESULT WINAPI ClassFactory_CreateInstance(IClassFactory *iface, IUnknown
 {
     CHECK_EXPECT(CreateInstance);
     ok(!outer, "outer = %p\n", outer);
-    ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", debugstr_guid(riid));
+    ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", wine_dbgstr_guid(riid));
     *ppv = &PersistMoniker;
     return S_OK;
 }
@@ -2365,7 +2353,7 @@ static HRESULT WINAPI ProtocolCF_QueryInterface(IClassFactory *iface, REFIID rii
     if(IsEqualGUID(&IID_IInternetProtocolInfo, riid))
         return E_NOINTERFACE;
 
-    ok(0, "unexpected riid %s\n", debugstr_guid(riid));
+    ok(0, "unexpected riid %s\n", wine_dbgstr_guid(riid));
     return E_NOTIMPL;
 }
 
@@ -2375,7 +2363,7 @@ static HRESULT WINAPI ProtocolCF_CreateInstance(IClassFactory *iface, IUnknown *
         return E_NOINTERFACE;
 
     todo_wine ok(outer != NULL, "outer == NULL\n");
-    todo_wine ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", debugstr_guid(riid));
+    todo_wine ok(IsEqualGUID(&IID_IUnknown, riid), "unexpected riid %s\n", wine_dbgstr_guid(riid));
     *ppv = &Protocol;
     return S_OK;
 }