diff --git a/reactos/dll/win32/advapi32/reg/reg.c b/reactos/dll/win32/advapi32/reg/reg.c
index c1feb0f62d1..337ddbe1790 100644
--- a/reactos/dll/win32/advapi32/reg/reg.c
+++ b/reactos/dll/win32/advapi32/reg/reg.c
@@ -1180,6 +1180,13 @@ RegDeleteKeyA (HKEY hKey,
   HANDLE TargetKey;
   NTSTATUS Status;
 
+  /* Make sure we got a subkey */
+  if (!lpSubKey)
+  {
+    /* Fail */
+    return ERROR_INVALID_PARAMETER;
+  }
+
   Status = MapDefaultKey (&ParentKey,
                           hKey);
   if (!NT_SUCCESS(Status))
@@ -1234,6 +1241,13 @@ RegDeleteKeyW (HKEY hKey,
   HANDLE TargetKey;
   NTSTATUS Status;
 
+  /* Make sure we got a subkey */
+  if (!lpSubKey)
+  {
+    /* Fail */
+    return ERROR_INVALID_PARAMETER;
+  }
+
   Status = MapDefaultKey (&ParentKey,
                           hKey);
   if (!NT_SUCCESS(Status))