diff --git a/packages/ensjs/src/utils/contentHash.test.ts b/packages/ensjs/src/utils/contentHash.test.ts
index e47facd5..fdca9c6b 100644
--- a/packages/ensjs/src/utils/contentHash.test.ts
+++ b/packages/ensjs/src/utils/contentHash.test.ts
@@ -129,4 +129,10 @@ describe('encodeContentHash', () => {
   it.each(displayArray)('$input => $encoded', ({ input, encoded }) => {
     expect(encodeContentHash(input)).toEqual(encoded)
   })
+  it('fails to encode onion with invalid length', () => {
+    expect(() => encodeContentHash('onion://123')).toThrow()
+  })
+  it('fails to encode onion3 with invalid length', () => {
+    expect(() => encodeContentHash('onion3://123')).toThrow()
+  })
 })
diff --git a/packages/ensjs/src/utils/contentHash.ts b/packages/ensjs/src/utils/contentHash.ts
index 18778913..3f95e7ea 100644
--- a/packages/ensjs/src/utils/contentHash.ts
+++ b/packages/ensjs/src/utils/contentHash.ts
@@ -92,5 +92,11 @@ export function encodeContentHash(text: string): Hex {
 
   const internalCodec = getInternalCodec(typeData.protocolType)
 
+  // manual exceptions for onion/onion3 which are just utf8 encoded
+  if (internalCodec === 'onion' && typeData.decoded.length !== 16)
+    throw new InvalidContentHashError()
+  if (internalCodec === 'onion3' && typeData.decoded.length !== 56)
+    throw new InvalidContentHashError()
+
   return `0x${encode(internalCodec, typeData.decoded)}`
 }