diff --git a/src/schemas/json/ruff.json b/src/schemas/json/ruff.json
index d6a8e9e870d..91bd251f946 100644
--- a/src/schemas/json/ruff.json
+++ b/src/schemas/json/ruff.json
@@ -130,6 +130,13 @@
         "$ref": "#/definitions/RuleSelector"
       }
     },
+    "extension": {
+      "description": "A mapping of custom file extensions to known file types (overridden\nby the `--extension` command-line flag).\n\nSupported file types include `python`, `pyi`, `ipynb`, and `markdown`.",
+      "type": ["object", "null"],
+      "additionalProperties": {
+        "$ref": "#/definitions/Language"
+      }
+    },
     "external": {
       "description": "A list of rule codes or prefixes that are unsupported by Ruff, but should be\npreserved when (e.g.) validating `# noqa` directives. Useful for\nretaining `# noqa` directives that cover plugins not yet implemented\nby Ruff.",
       "type": ["array", "null"],
@@ -1600,6 +1607,10 @@
       },
       "additionalProperties": false
     },
+    "Language": {
+      "type": "string",
+      "enum": ["python", "pyi", "ipynb", "markdown"]
+    },
     "LineEnding": {
       "oneOf": [
         {