diff --git a/src/commands/options.ts b/src/commands/options.ts
index 99d6ae6..3eb72b0 100644
--- a/src/commands/options.ts
+++ b/src/commands/options.ts
@@ -26,6 +26,7 @@ const ajvOptions: SchemaMap = {
   multipleOfPrecision: boolOrNat,
   messages: {type: "boolean"},
   [`${CODE}es5`]: {type: "boolean"},
+  [`${CODE}esm`]: {type: "boolean"},
   [`${CODE}lines`]: {type: "boolean"},
   [`${CODE}optimize`]: boolOrNat,
   [`${CODE}formats`]: {type: "string"},