diff --git a/dlls/ole32/tests/compobj.c b/dlls/ole32/tests/compobj.c
index b6150347030..c23a4d72878 100644
--- a/dlls/ole32/tests/compobj.c
+++ b/dlls/ole32/tests/compobj.c
@@ -77,18 +77,6 @@ static const WCHAR progidW[] = {'P','r','o','g','I','d','.','P','r','o','g','I',
 DEFINE_GUID(IID_IWineTest, 0x5201163f, 0x8164, 0x4fd0, 0xa1, 0xa2, 0x5d, 0x5a, 0x36, 0x54, 0xd3, 0xbd);
 DEFINE_GUID(CLSID_WineOOPTest, 0x5201163f, 0x8164, 0x4fd0, 0xa1, 0xa2, 0x5d, 0x5a, 0x36, 0x54, 0xd3, 0xbd);
 
-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 LONG cLocks;
 
 static void LockModule(void)
@@ -381,7 +369,7 @@ static void test_CLSIDFromProgID(void)
         hr = CLSIDFromProgID(progidW, &clsid);
         /* it returns generated CLSID here */
         ok(!IsEqualCLSID(&clsid, &CLSID_non_existent) && !IsEqualCLSID(&clsid, &CLSID_NULL),
-                 "got wrong clsid %s\n", debugstr_guid(&clsid));
+                 "got wrong clsid %s\n", wine_dbgstr_guid(&clsid));
 
         /* duplicate progid present in context - returns generated guid here too */
         clsid = CLSID_NULL;
@@ -391,7 +379,7 @@ static void test_CLSIDFromProgID(void)
         /* that's where it differs from StdFont */
         clsid1.Data4[7] = 0x52;
         ok(!IsEqualCLSID(&clsid, &CLSID_StdFont) && !IsEqualCLSID(&clsid, &CLSID_NULL) && !IsEqualCLSID(&clsid, &clsid1),
-            "got %s\n", debugstr_guid(&clsid));
+            "got %s\n", wine_dbgstr_guid(&clsid));
 
         pDeactivateActCtx(0, cookie);
         pReleaseActCtx(handle);
@@ -1034,22 +1022,22 @@ static void test_CoGetPSClsid(void)
         memset(&clsid, 0, sizeof(clsid));
         hr = CoGetPSClsid(&IID_Testiface, &clsid);
         ok(hr == S_OK, "got 0x%08x\n", hr);
-        ok(IsEqualGUID(&clsid, &IID_Testiface), "got clsid %s\n", debugstr_guid(&clsid));
+        ok(IsEqualGUID(&clsid, &IID_Testiface), "got clsid %s\n", wine_dbgstr_guid(&clsid));
 
         memset(&clsid, 0, sizeof(clsid));
         hr = CoGetPSClsid(&IID_Testiface2, &clsid);
         ok(hr == S_OK, "got 0x%08x\n", hr);
-        ok(IsEqualGUID(&clsid, &IID_Testiface2), "got clsid %s\n", debugstr_guid(&clsid));
+        ok(IsEqualGUID(&clsid, &IID_Testiface2), "got clsid %s\n", wine_dbgstr_guid(&clsid));
 
         memset(&clsid, 0, sizeof(clsid));
         hr = CoGetPSClsid(&IID_Testiface3, &clsid);
         ok(hr == S_OK, "got 0x%08x\n", hr);
-        ok(IsEqualGUID(&clsid, &IID_TestPS), "got clsid %s\n", debugstr_guid(&clsid));
+        ok(IsEqualGUID(&clsid, &IID_TestPS), "got clsid %s\n", wine_dbgstr_guid(&clsid));
 
         memset(&clsid, 0xaa, sizeof(clsid));
         hr = CoGetPSClsid(&IID_Testiface4, &clsid);
         ok(hr == S_OK, "got 0x%08x\n", hr);
-        ok(IsEqualGUID(&clsid, &GUID_NULL), "got clsid %s\n", debugstr_guid(&clsid));
+        ok(IsEqualGUID(&clsid, &GUID_NULL), "got clsid %s\n", wine_dbgstr_guid(&clsid));
 
         /* register same interface and try to get CLSID back */
         hr = CoRegisterPSClsid(&IID_Testiface, &IID_Testiface4);
@@ -1057,7 +1045,7 @@ static void test_CoGetPSClsid(void)
         memset(&clsid, 0, sizeof(clsid));
         hr = CoGetPSClsid(&IID_Testiface, &clsid);
         ok(hr == S_OK, "got 0x%08x\n", hr);
-        ok(IsEqualGUID(&clsid, &IID_Testiface4), "got clsid %s\n", debugstr_guid(&clsid));
+        ok(IsEqualGUID(&clsid, &IID_Testiface4), "got clsid %s\n", wine_dbgstr_guid(&clsid));
 
         pDeactivateActCtx(0, cookie);
         pReleaseActCtx(handle);
diff --git a/dlls/ole32/tests/defaulthandler.c b/dlls/ole32/tests/defaulthandler.c
index efbd43103be..60bc29c08dd 100644
--- a/dlls/ole32/tests/defaulthandler.c
+++ b/dlls/ole32/tests/defaulthandler.c
@@ -64,18 +64,6 @@ DEFINE_EXPECT(CF_QueryInterface_ClassFactory);
 DEFINE_EXPECT(CF_CreateInstance);
 DEFINE_EXPECT(CF_QueryInterface_IMarshal);
 
-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 HRESULT create_storage(IStorage **stg)
 {
     HRESULT hr;
@@ -194,7 +182,7 @@ static HRESULT WINAPI ClassFactory_QueryInterface(IClassFactory *iface, REFIID r
         return S_OK;
     }
 
-    ok(0, "unexpected interface: %s\n", debugstr_guid(riid));
+    ok(0, "unexpected interface: %s\n", wine_dbgstr_guid(riid));
     *ppv = NULL;
     return E_NOINTERFACE;
 }
@@ -215,7 +203,7 @@ static HRESULT WINAPI ClassFactory_CreateInstance(IClassFactory *iface,
     CHECK_EXPECT(CF_CreateInstance);
 
     ok(pUnkOuter == NULL, "pUnkOuter != NULL\n");
-    todo_wine ok(IsEqualGUID(riid, &IID_IUnknown), "riid = %s\n", debugstr_guid(riid));
+    todo_wine ok(IsEqualGUID(riid, &IID_IUnknown), "riid = %s\n", wine_dbgstr_guid(riid));
     if(IsEqualGUID(riid, &IID_IOleObject)) {
         *ppv = NULL;
         return E_NOINTERFACE;
diff --git a/dlls/ole32/tests/ole_server.c b/dlls/ole32/tests/ole_server.c
index 7a9dc30427d..77abda47aaf 100644
--- a/dlls/ole32/tests/ole_server.c
+++ b/dlls/ole32/tests/ole_server.c
@@ -65,7 +65,6 @@ static LONG obj_ref, class_ref, server_locks;
 
 static const char *debugstr_guid(const GUID *guid)
 {
-    static char buf[50];
     int i;
 
     if (!guid) return "(null)";
@@ -76,11 +75,7 @@ static const char *debugstr_guid(const GUID *guid)
             return guid_name[i].name;
     }
 
-    sprintf(buf, "{%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x}",
-            guid->Data1, guid->Data2, guid->Data3, guid->Data4[0],
-            guid->Data4[1], guid->Data4[2], guid->Data4[3], guid->Data4[4],
-            guid->Data4[5], guid->Data4[6], guid->Data4[7]);
-    return buf;
+    return wine_dbgstr_guid(guid);
 }
 
 /******************************* OLE server *******************************/