diff --git a/dlls/mapi32/mapi32.spec b/dlls/mapi32/mapi32.spec
index 74a96bba223..fb504635b79 100644
--- a/dlls/mapi32/mapi32.spec
+++ b/dlls/mapi32/mapi32.spec
@@ -14,7 +14,7 @@
 @ stub CloseIMsgSession@4
 @ stub CreateIProp@24
 @ stub CreateTable@36
-@ stub DeinitMapiUtil@0
+@ stdcall DeinitMapiUtil() DeinitMapiUtil
 @ stub DeregisterIdleRoutine@4
 @ stub DllCanUnloadNow
 @ stub DllGetClassObject
diff --git a/dlls/mapi32/mapi32_main.c b/dlls/mapi32/mapi32_main.c
index 1d1c4eb3180..634287542c5 100644
--- a/dlls/mapi32/mapi32_main.c
+++ b/dlls/mapi32/mapi32_main.c
@@ -53,7 +53,12 @@ lpszPassword, FLAGS flFlags, VOID* lppSession)
     return MAPI_E_LOGON_FAILURE;
 }
 
-VOID WINAPI MAPIUninitialize()
+VOID WINAPI MAPIUninitialize(void)
+{
+    ERR("Stub\n");
+}
+
+VOID WINAPI DeinitMapiUtil(void)
 {
     ERR("Stub\n");
 }