diff --git a/framework/src/modules/dpos/random_seed.ts b/framework/src/modules/dpos/random_seed.ts
index 31629304fb3..3b133008ffc 100644
--- a/framework/src/modules/dpos/random_seed.ts
+++ b/framework/src/modules/dpos/random_seed.ts
@@ -56,7 +56,7 @@ const bitwiseXOR = (bufferArray: Buffer[]): Buffer => {
 	return result;
 };
 
-const findPreviousHeaderOfDelegate = (
+export const findPreviousHeaderOfDelegate = (
 	header: BlockHeader,
 	searchTillHeight: number,
 	headersMap: HeadersMap,
@@ -65,6 +65,10 @@ const findPreviousHeaderOfDelegate = (
 	const searchTill = Math.max(searchTillHeight, 1);
 
 	for (let i = height - 1; i >= searchTill; i -= 1) {
+		const foundHeader = headersMap[i];
+		if (!foundHeader) {
+			return undefined;
+		}
 		if (headersMap[i].generatorPublicKey.equals(generatorPublicKey)) {
 			return headersMap[i];
 		}
diff --git a/framework/test/unit/modules/dpos/random_seed.spec.ts b/framework/test/unit/modules/dpos/random_seed.spec.ts
index 8d207bf8533..d828fcdee65 100644
--- a/framework/test/unit/modules/dpos/random_seed.spec.ts
+++ b/framework/test/unit/modules/dpos/random_seed.spec.ts
@@ -13,12 +13,16 @@
  */
 
 import { BlockHeader } from '@liskhq/lisk-chain';
+import { getRandomBytes } from '@liskhq/lisk-cryptography';
 import * as randomSeedFirstRound from '../../../fixtures/dpos_random_seed_generation/dpos_random_seed_generation_first_round.json';
 import * as randomSeedsMultipleRounds from '../../../fixtures/dpos_random_seed_generation/dpos_random_seed_generation_other_rounds.json';
 import * as randomSeedsInvalidSeedReveal from '../../../fixtures/dpos_random_seed_generation/dpos_random_seed_generation_invalid_seed_reveal.json';
 import * as randomSeedsNotForgedEarlier from '../../../fixtures/dpos_random_seed_generation/dpos_random_seed_generation_not_forged_earlier.json';
 
-import { generateRandomSeeds } from '../../../../src/modules/dpos/random_seed';
+import {
+	generateRandomSeeds,
+	findPreviousHeaderOfDelegate,
+} from '../../../../src/modules/dpos/random_seed';
 import { Rounds } from '../../../../src/modules/dpos/rounds';
 
 const generateHeadersFromTest = (blocks: any): BlockHeader[] =>
@@ -70,4 +74,49 @@ describe('random_seed', () => {
 			},
 		);
 	});
+
+	describe('findPreviousHeaderOfDelegate', () => {
+		describe('when previously generated block exist in header map', () => {
+			it('should return the header', () => {
+				const generatorPublicKey = Buffer.from('some-generator', 'utf8');
+				const expectedHeader = { generatorPublicKey, height: 320 } as BlockHeader;
+				const result = findPreviousHeaderOfDelegate(
+					{ height: 321, generatorPublicKey } as any,
+					320,
+					{ [expectedHeader.height]: expectedHeader },
+				);
+				expect(result).toBe(expectedHeader);
+			});
+		});
+		describe('when previously generated block does not exist in header map', () => {
+			it('should return undefined', () => {
+				const generatorPublicKey = Buffer.from('some-generator', 'utf8');
+				const result = findPreviousHeaderOfDelegate(
+					{ height: 321, generatorPublicKey } as any,
+					319,
+					{
+						320: { generatorPublicKey: getRandomBytes(32), height: 320 } as BlockHeader,
+						319: { generatorPublicKey: getRandomBytes(32), height: 319 } as BlockHeader,
+					},
+				);
+				expect(result).toBeUndefined();
+			});
+		});
+
+		describe('when the header map does not include all the height until searchTill', () => {
+			it('should return undefined', () => {
+				const generatorPublicKey = Buffer.from('some-generator', 'utf8');
+				const result = findPreviousHeaderOfDelegate(
+					{ height: 321, generatorPublicKey } as any,
+					300,
+					{
+						320: { generatorPublicKey: getRandomBytes(32), height: 320 } as BlockHeader,
+						319: { generatorPublicKey: getRandomBytes(32), height: 319 } as BlockHeader,
+						318: { generatorPublicKey: getRandomBytes(32), height: 319 } as BlockHeader,
+					},
+				);
+				expect(result).toBeUndefined();
+			});
+		});
+	});
 });