diff --git a/programs/reg/reg.c b/programs/reg/reg.c
index 7ed45b73ad8..69107d54b92 100644
--- a/programs/reg/reg.c
+++ b/programs/reg/reg.c
@@ -234,9 +234,6 @@ BOOL parse_registry_key(const WCHAR *key, HKEY *root, WCHAR **path)
     if (!sane_path(key))
         return FALSE;
 
-    *path = wcschr(key, '\\');
-    if (*path) (*path)++;
-
     *root = path_get_rootkey(key);
     if (!*root)
     {
@@ -244,6 +241,19 @@ BOOL parse_registry_key(const WCHAR *key, HKEY *root, WCHAR **path)
         return FALSE;
     }
 
+    *path = wcschr(key, '\\');
+
+    if (!*path)
+        return TRUE;
+
+    (*path)++;
+
+    if (!**path)
+    {
+        output_message(STRING_INVALID_SYSTEM_KEY);
+        return FALSE;
+    }
+
     return TRUE;
 }
 
diff --git a/programs/reg/tests/add.c b/programs/reg/tests/add.c
index 36b5f821350..6973eefd892 100644
--- a/programs/reg/tests/add.c
+++ b/programs/reg/tests/add.c
@@ -311,12 +311,12 @@ static void test_key_formats(void)
 
     /* Test validity of trailing backslash after system key */
     run_reg_exe("reg add HKCU\\ /v Value1 /t REG_SZ /d foo /f", &r);
-    todo_wine ok(r == REG_EXIT_FAILURE, "got exit code %d, expected 1\n", r);
-    todo_wine verify_reg_nonexist(HKEY_CURRENT_USER, "Value1");
+    ok(r == REG_EXIT_FAILURE, "got exit code %d, expected 1\n", r);
+    verify_reg_nonexist(HKEY_CURRENT_USER, "Value1");
 
     run_reg_exe("reg add HKEY_CURRENT_USER\\ /v Value2 /t REG_SZ /d bar /f", &r);
-    todo_wine ok(r == REG_EXIT_FAILURE, "got exit code %d, expected 1\n", r);
-    todo_wine verify_reg_nonexist(HKEY_CURRENT_USER, "Value2");
+    ok(r == REG_EXIT_FAILURE, "got exit code %d, expected 1\n", r);
+    verify_reg_nonexist(HKEY_CURRENT_USER, "Value2");
 }
 
 static void test_add(void)