diff --git a/packages/techdocs-container/techdocs-core/src/core.py b/packages/techdocs-container/techdocs-core/src/core.py
index aa94d870bc..7e5385e9f5 100644
--- a/packages/techdocs-container/techdocs-core/src/core.py
+++ b/packages/techdocs-container/techdocs-core/src/core.py
@@ -95,7 +95,7 @@ class TechDocsCore(BasePlugin):
         config["markdown_extensions"].append("markdown_inline_graphviz")
         config["markdown_extensions"].append("plantuml_markdown")
 
-        # merge or add config supplied by user in the mkdocs.yml
+        # merge config supplied by user in the mkdocs.yml
         mdx_configs_keys = config["mdx_configs"].keys()
         mdx_configs_override_keys = mdx_configs_override.keys()
         for key in mdx_configs_override_keys:
@@ -103,9 +103,5 @@ class TechDocsCore(BasePlugin):
                 default_config = config["mdx_configs"][key]
                 override_config = mdx_configs_override[key]
                 default_config.update(override_config)
-                config["mdx_configs"][key] = default_config
-            else:
-                config["mdx_configs"].append(key)
-                config["mdx_configs"][key] = mdx_configs_override[key]
 
         return config
diff --git a/packages/techdocs-container/techdocs-core/src/test_core.py b/packages/techdocs-container/techdocs-core/src/test_core.py
index 7f34d28d38..0ccdc713e6 100644
--- a/packages/techdocs-container/techdocs-core/src/test_core.py
+++ b/packages/techdocs-container/techdocs-core/src/test_core.py
@@ -37,12 +37,3 @@ class TestTechDocsCoreConfig(unittest.TestCase):
         self.assertTrue("toc"  in final_config["mdx_configs"])
         self.assertTrue("permalink"  in final_config["mdx_configs"]["toc"])
         self.assertFalse(final_config["mdx_configs"]["toc"]["permalink"])
-
-    def test_add_user_config_to_default_config(self):
-        self.mkdocs_yaml_config["markdown_extension"] = []
-        self.mkdocs_yaml_config["mdx_configs"] = {}
-        self.mkdocs_yaml_config["markdown_extension"].append(["abc"])
-        self.mkdocs_yaml_config["mdx_configs"]["abc"] = {"testkey": "testvalue"}
-        final_config = self.techdocscore.on_config(self.mkdocs_yaml_config)
-        self.assertTrue("abc"  in final_config["mdx_configs"])
-        self.assertTrue("testkey"  in final_config["mdx_configs"]["abc"])