diff --git a/dlls/user32/dde_client.c b/dlls/user32/dde_client.c
index 16e6daa..fe2dada 100644
--- a/dlls/user32/dde_client.c
+++ b/dlls/user32/dde_client.c
@@ -1141,8 +1141,13 @@ HDDEDATA WINAPI DdeClientTransaction(LPBYTE pData, DWORD cbData, HCONV hConv, HS
 	pXAct = WDML_ClientQueueExecute(pConv, pData, cbData);
 	break;
     case XTYP_POKE:
-	pXAct = WDML_ClientQueuePoke(pConv, pData, cbData, wFmt, hszItem);
-	break;
+        if (!hszItem)
+        {
+            pConv->instance->lastError = DMLERR_INVALIDPARAMETER;
+            return 0;
+        }
+        pXAct = WDML_ClientQueuePoke(pConv, pData, cbData, wFmt, hszItem);
+        break;
     case XTYP_ADVSTART|XTYPF_NODATA:
     case XTYP_ADVSTART|XTYPF_NODATA|XTYPF_ACKREQ:
     case XTYP_ADVSTART:
diff --git a/dlls/user32/tests/dde.c b/dlls/user32/tests/dde.c
index b36a4bd..035ff69 100644
--- a/dlls/user32/tests/dde.c
+++ b/dlls/user32/tests/dde.c
@@ -353,10 +353,7 @@ static void test_ddeml_client(void)
     ret = DdeGetLastError(client_pid);
     ok(op == NULL, "Expected NULL, got %p\n", op);
     ok(res == 0xdeadbeef, "Expected 0xdeadbeef, got %d\n", res);
-    todo_wine
-    {
-        ok(ret == DMLERR_INVALIDPARAMETER, "Expected DMLERR_INVALIDPARAMETER, got %d\n", ret);
-    }
+    ok(ret == DMLERR_INVALIDPARAMETER, "Expected DMLERR_INVALIDPARAMETER, got %d\n", ret);
 
     /* XTYP_POKE, no data */
     res = 0xdeadbeef;
@@ -365,10 +362,7 @@ static void test_ddeml_client(void)
     ret = DdeGetLastError(client_pid);
     ok(op == NULL, "Expected NULL, got %p\n", op);
     ok(res == 0xdeadbeef, "Expected 0xdeadbeef, got %d\n", res);
-    todo_wine
-    {
-        ok(ret == DMLERR_INVALIDPARAMETER, "Expected DMLERR_INVALIDPARAMETER, got %d\n", ret);
-    }
+    ok(ret == DMLERR_INVALIDPARAMETER, "Expected DMLERR_INVALIDPARAMETER, got %d\n", ret);
 
     /* XTYP_POKE, wrong size */
     res = 0xdeadbeef;
-- 
1.4.4.2