diff --git a/src/index.ts b/src/index.ts
index 9ce9534..0e5f485 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -47,7 +47,7 @@ export function sign(secretKey: Uint8Array, messageHash: Uint8Array): Buffer {
  * @param signatures
  */
 export function aggregateSignatures(signatures: Uint8Array[]): Buffer {
-  assert(signatures, "signatures is null or undefined");
+  assert(signatures && signatures.length > 0, "signatures is null or undefined or empty array");
   return Signature.aggregate(
     signatures.map((signature): Signature => {
       return Signature.fromCompressedBytes(signature);
diff --git a/test/spec/aggregate_sigs.test.ts b/test/spec/aggregate_sigs.test.ts
index 3d9191e..139522f 100644
--- a/test/spec/aggregate_sigs.test.ts
+++ b/test/spec/aggregate_sigs.test.ts
@@ -20,10 +20,17 @@ describeDirectorySpecTest<IAggregateSigsTestCase, string>(
     "../../node_modules/@chainsafe/eth2-spec-tests/tests/general/phase0/bls/aggregate/small"
   ),
   (testCase => {
-    const result =  bls.aggregateSignatures(testCase.data.input.map(pubKey => {
-      return Buffer.from(pubKey.replace("0x", ""), "hex");
-    }));
-    return `0x${result.toString("hex")}`;
+    try {
+      const result =  bls.aggregateSignatures(testCase.data.input.map(pubKey => {
+        return Buffer.from(pubKey.replace("0x", ""), "hex");
+      }));
+      return `0x${result.toString("hex")}`;
+    } catch (e) {
+      if(e.message === "signatures is null or undefined or empty array") {
+        return null;
+      }
+      throw e;
+    }
   }),
   {
     inputTypes: {
diff --git a/test/spec/aggregate_sigs_verify.test.ts b/test/spec/aggregate_sigs_verify.test.ts
index c6d2dd8..4f8c122 100644
--- a/test/spec/aggregate_sigs_verify.test.ts
+++ b/test/spec/aggregate_sigs_verify.test.ts
@@ -5,10 +5,8 @@ import {describeDirectorySpecTest, InputType} from "@chainsafe/lodestar-spec-tes
 interface AggregateSigsVerifyTestCase {
   data: {
     input: {
-      pairs: [{
-        pubkey: string;
-        message: string;
-      }];
+      pubkeys: string[];
+      messages: string[];
       signature: string;
     };
     output: boolean;
@@ -30,11 +28,11 @@ describeDirectorySpecTest<AggregateSigsVerifyTestCase, boolean>(
     "../../node_modules/@chainsafe/eth2-spec-tests/tests/general/phase0/bls/aggregate_verify/small"
   ),
   (testCase => {
-    const pubkeys = testCase.data.input.pairs.map(pair => {
-      return Buffer.from(pair.pubkey.replace("0x", ""), "hex");
+    const pubkeys = testCase.data.input.pubkeys.map(pubkey => {
+      return Buffer.from(pubkey.replace("0x", ""), "hex");
     });
-    const messages = testCase.data.input.pairs.map(pair => {
-      return Buffer.from(pair.message.replace("0x", ""), "hex");
+    const messages = testCase.data.input.messages.map(msg => {
+      return Buffer.from(msg.replace("0x", ""), "hex");
     });
     return bls.verifyMultiple(
       pubkeys,