diff --git a/dlls/advapi32/registry.c b/dlls/advapi32/registry.c
index 52de6c5d427..3762908aff1 100644
--- a/dlls/advapi32/registry.c
+++ b/dlls/advapi32/registry.c
@@ -381,6 +381,9 @@ LSTATUS WINAPI RegOpenKeyExA( HKEY hkey, LPCSTR name, DWORD reserved, REGSAM acc
  */
 LSTATUS WINAPI RegOpenKeyW( HKEY hkey, LPCWSTR name, PHKEY retkey )
 {
+    if (!retkey)
+        return ERROR_INVALID_PARAMETER;
+
     if (!name || !*name)
     {
         *retkey = hkey;
@@ -402,10 +405,13 @@ LSTATUS WINAPI RegOpenKeyW( HKEY hkey, LPCWSTR name, PHKEY retkey )
  *
  * RETURNS
  *  Success: ERROR_SUCCESS
- *  Failure: A standard Win32 error code. retkey is set to 0.
+ *  Failure: A standard Win32 error code. When retkey is valid, *retkey is set to 0.
  */
 LSTATUS WINAPI RegOpenKeyA( HKEY hkey, LPCSTR name, PHKEY retkey )
 {
+    if (!retkey)
+        return ERROR_INVALID_PARAMETER;
+
     if (!name || !*name)
     {
         *retkey = hkey;
diff --git a/dlls/advapi32/tests/registry.c b/dlls/advapi32/tests/registry.c
index 47e76b28634..ca82fa13186 100644
--- a/dlls/advapi32/tests/registry.c
+++ b/dlls/advapi32/tests/registry.c
@@ -956,9 +956,18 @@ static void test_reg_open_key(void)
     RegCloseKey(hkResult);
 
     /* send in NULL hkResult */
+    SetLastError(0xdeadbeef);
     ret = RegOpenKeyA(HKEY_CURRENT_USER, "Software\\Wine\\Test", NULL);
     ok(ret == ERROR_INVALID_PARAMETER, "expected ERROR_INVALID_PARAMETER, got %d\n", ret);
 
+    SetLastError(0xdeadbeef);
+    ret = RegOpenKeyA(HKEY_CURRENT_USER, NULL, NULL);
+    ok(ret == ERROR_INVALID_PARAMETER, "expected ERROR_INVALID_PARAMETER, got %d\n", ret);
+
+    SetLastError(0xdeadbeef);
+    ret = RegOpenKeyA(NULL, NULL, NULL);
+    ok(ret == ERROR_INVALID_PARAMETER, "expected ERROR_INVALID_PARAMETER, got %d\n", ret);
+
     /*  beginning backslash character */
     ret = RegOpenKeyA(HKEY_CURRENT_USER, "\\Software\\Wine\\Test", &hkResult);
        ok(ret == ERROR_BAD_PATHNAME || /* NT/2k/XP */