diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1617e6f37db..488cbdc82840 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ Changes:
 - Added support for typegen over `Range/RangeInclusive` types
 - Add explicit support for `Call` typegen (inclusive of non-defaults)
 - Deupe `wss://` handling in `polkadot-types-from-{chain, defs}`
+- Allow for optional `definitions.ts` in typegen (only use chain)
 
 
 ## 8.3.2 May 8, 2022
diff --git a/packages/typegen/src/fromChain.ts b/packages/typegen/src/fromChain.ts
index 2b18807a9075..7ec75aedd804 100644
--- a/packages/typegen/src/fromChain.ts
+++ b/packages/typegen/src/fromChain.ts
@@ -10,37 +10,44 @@ import { Definitions } from '@polkadot/types/types';
 import { formatNumber } from '@polkadot/util';
 
 import { generateDefaultConsts, generateDefaultErrors, generateDefaultEvents, generateDefaultQuery, generateDefaultRpc, generateDefaultTx } from './generate';
-import { getMetadataViaWs, HEADER, writeFile } from './util';
+import { assertDir, assertFile, getMetadataViaWs, HEADER, writeFile } from './util';
 
 function generate (metaHex: HexString, pkg: string | undefined, output: string, isStrict?: boolean): void {
   console.log(`Generating from metadata, ${formatNumber((metaHex.length - 2) / 2)} bytes`);
 
-  const base = path.join(process.cwd(), output);
-  const extraTypes = pkg
-    // eslint-disable-next-line @typescript-eslint/no-var-requires
-    ? { [pkg]: require(path.join(base, 'definitions')) as Record<string, any> }
-    : {};
+  const outputPath = assertDir(path.join(process.cwd(), output));
+  let extraTypes: Record<string, any> = {};
+  let customLookupDefinitions: Definitions = { rpc: {}, types: {} };
 
-  let customLookupDefinitions;
+  if (pkg) {
+    try {
+      extraTypes = {
+        // eslint-disable-next-line @typescript-eslint/no-var-requires, @typescript-eslint/no-unsafe-argument
+        [pkg]: require(assertFile(path.join(outputPath, 'definitions.ts'))) as Record<string, any>
+      };
+    } catch (error) {
+      console.error('ERROR: No custom definitions found:', (error as Error).message);
+    }
+  }
 
   try {
     customLookupDefinitions = {
       rpc: {},
       // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access, @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-var-requires
-      types: require(path.join(base, 'lookup.ts')).default
-    } as Definitions;
+      types: require(assertFile(path.join(outputPath, 'lookup.ts'))).default
+    };
   } catch (error) {
-    console.log('No custom definitions found.');
+    console.error('ERROR: No lookup definitions found:', (error as Error).message);
   }
 
-  generateDefaultConsts(path.join(base, 'augment-api-consts.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
-  generateDefaultErrors(path.join(base, 'augment-api-errors.ts'), metaHex, extraTypes, isStrict);
-  generateDefaultEvents(path.join(base, 'augment-api-events.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
-  generateDefaultQuery(path.join(base, 'augment-api-query.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
-  generateDefaultRpc(path.join(base, 'augment-api-rpc.ts'), extraTypes);
-  generateDefaultTx(path.join(base, 'augment-api-tx.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
+  generateDefaultConsts(path.join(outputPath, 'augment-api-consts.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
+  generateDefaultErrors(path.join(outputPath, 'augment-api-errors.ts'), metaHex, extraTypes, isStrict);
+  generateDefaultEvents(path.join(outputPath, 'augment-api-events.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
+  generateDefaultQuery(path.join(outputPath, 'augment-api-query.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
+  generateDefaultRpc(path.join(outputPath, 'augment-api-rpc.ts'), extraTypes);
+  generateDefaultTx(path.join(outputPath, 'augment-api-tx.ts'), metaHex, extraTypes, isStrict, customLookupDefinitions);
 
-  writeFile(path.join(base, 'augment-api.ts'), (): string =>
+  writeFile(path.join(outputPath, 'augment-api.ts'), (): string =>
     [
       HEADER('chain'),
       ...[
@@ -82,6 +89,6 @@ export function main (): void {
       .catch(() => process.exit(1));
   } else {
     // eslint-disable-next-line @typescript-eslint/no-var-requires
-    generate((require(path.join(process.cwd(), endpoint)) as Record<string, HexString>).result, pkg, output, isStrict);
+    generate((require(assertFile(path.join(process.cwd(), endpoint))) as Record<string, HexString>).result, pkg, output, isStrict);
   }
 }
diff --git a/packages/typegen/src/fromDefs.ts b/packages/typegen/src/fromDefs.ts
index 14cb491ab485..0796dfd120fb 100644
--- a/packages/typegen/src/fromDefs.ts
+++ b/packages/typegen/src/fromDefs.ts
@@ -11,7 +11,7 @@ import * as substrateDefs from '@polkadot/types/interfaces/definitions';
 import { generateInterfaceTypes } from './generate/interfaceRegistry';
 import { generateTsDef } from './generate/tsDef';
 import { generateDefaultLookup } from './generate';
-import { getMetadataViaWs } from './util';
+import { assertDir, assertFile, getMetadataViaWs } from './util';
 
 type ArgV = { input: string; package: string; endpoint?: string; };
 
@@ -33,8 +33,16 @@ export function main (): void {
     }
   }).argv as ArgV;
 
-  // eslint-disable-next-line @typescript-eslint/no-var-requires
-  const userDefs = require(path.join(process.cwd(), input, 'definitions.ts')) as Record<string, any>;
+  const inputPath = assertDir(path.join(process.cwd(), input));
+  let userDefs: Record<string, any> = {};
+
+  try {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    userDefs = require(assertFile(path.join(inputPath, 'definitions.ts'))) as Record<string, any>;
+  } catch (error) {
+    console.error('ERROR: Unable to load user definitions:', (error as Error).message);
+  }
+
   const userKeys = Object.keys(userDefs);
   const filteredBase = Object
     .entries(substrateDefs as Record<string, unknown>)
@@ -57,7 +65,6 @@ export function main (): void {
     '@polkadot/types/interfaces': filteredBase,
     [pkg]: userDefs
   };
-  const inputPath = path.join(process.cwd(), input);
 
   generateTsDef(allDefs, inputPath, pkg);
   generateInterfaceTypes(allDefs, path.join(inputPath, 'augment-types.ts'));
@@ -69,7 +76,7 @@ export function main (): void {
         .catch(() => process.exit(1));
     } else {
       // eslint-disable-next-line @typescript-eslint/no-var-requires
-      const metaHex = (require(path.join(process.cwd(), endpoint)) as Record<string, HexString>).result;
+      const metaHex = (require(assertFile(path.join(process.cwd(), endpoint))) as Record<string, HexString>).result;
 
       generateDefaultLookup(inputPath, metaHex);
     }
diff --git a/packages/typegen/src/util/assert.ts b/packages/typegen/src/util/assert.ts
new file mode 100644
index 000000000000..02bc065ab7dd
--- /dev/null
+++ b/packages/typegen/src/util/assert.ts
@@ -0,0 +1,18 @@
+// Copyright 2017-2022 @polkadot/typegen authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+import fs from 'fs';
+
+import { assert } from '@polkadot/util';
+
+export function assertDir (path: string): string {
+  assert(fs.existsSync(path) && fs.lstatSync(path).isDirectory(), `${path} is not a directory`);
+
+  return path;
+}
+
+export function assertFile (path: string): string {
+  assert(fs.existsSync(path) && fs.lstatSync(path).isFile(), `${path} is not a file`);
+
+  return path;
+}
diff --git a/packages/typegen/src/util/index.ts b/packages/typegen/src/util/index.ts
index 4073ae3344c5..1aa0d7c593f1 100644
--- a/packages/typegen/src/util/index.ts
+++ b/packages/typegen/src/util/index.ts
@@ -1,6 +1,7 @@
 // Copyright 2017-2022 @polkadot/typegen authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+export * from './assert';
 export * from './derived';
 export * from './docs';
 export * from './file';