diff --git a/dlls/ole32/compobj.c b/dlls/ole32/compobj.c
index eae2d18f081..d39c3ad12cf 100644
--- a/dlls/ole32/compobj.c
+++ b/dlls/ole32/compobj.c
@@ -2233,3 +2233,19 @@ BOOL WINAPI IsEqualGUID(
 {
     return !memcmp(rguid1,rguid2,sizeof(GUID));
 }
+
+/***********************************************************************
+ *           CoInitializeSecurity [OLE32.@]
+ */
+HRESULT WINAPI CoInitializeSecurity(PSECURITY_DESCRIPTOR pSecDesc, LONG cAuthSvc,
+                                    SOLE_AUTHENTICATION_SERVICE* asAuthSvc,
+                                    void* pReserved1, DWORD dwAuthnLevel,
+                                    DWORD dwImpLevel, void* pReserved2,
+                                    DWORD dwCapabilities, void* pReserved3)
+{
+  FIXME("(%p,%ld,%p,%p,%ld,%ld,%p,%ld,%p) - stub!\n", pSecDesc, cAuthSvc,
+        asAuthSvc, pReserved1, dwAuthnLevel, dwImpLevel, pReserved2,
+        dwCapabilities, pReserved3);
+  return S_OK;
+}
+
diff --git a/dlls/ole32/ole32.spec b/dlls/ole32/ole32.spec
index 2602527a1d5..8d1bfd9182b 100644
--- a/dlls/ole32/ole32.spec
+++ b/dlls/ole32/ole32.spec
@@ -163,7 +163,7 @@ init	OLE32_DllEntryPoint
 161 stub WriteOleStg
 162 stub WriteStringStream
 163 stdcall CoInitializeEx(ptr long) CoInitializeEx
-164 stub CoInitializeSecurity       # stdcall (ptr long ptr ptr long long ptr long ptr) return 0,ERR_NOTIMPLEMENTED
+164 stdcall CoInitializeSecurity(ptr long ptr ptr long long ptr long ptr) CoInitializeSecurity
 165 stdcall CoCreateInstanceEx(ptr ptr long ptr long ptr) CoCreateInstanceEx
 166 stdcall PropVariantClear(ptr) PropVariantClear
 167 stub CoCopyProxy                # stdcall (ptr ptr) return 0,ERR_NOTIMPLEMENTED