diff --git a/lib/frost.rb b/lib/frost.rb
index fea792d..6e79eb1 100644
--- a/lib/frost.rb
+++ b/lib/frost.rb
@@ -119,6 +119,7 @@ def sign(secret_share, group_pubkey, nonces, msg, commitment_list)
   def aggregate(commitment_list, msg, group_pubkey, sig_shares)
     raise ArgumentError, "msg must be String." unless msg.is_a?(String)
     raise ArgumentError, "group_pubkey must be ECDSA::Point." unless group_pubkey.is_a?(ECDSA::Point)
+    raise ArgumentError, "The numbers of commitment_list and sig_shares do not match." unless commitment_list.length == sig_shares.length
 
     binding_factors = compute_binding_factors(group_pubkey, commitment_list, msg)
     group_commitment = compute_group_commitment(commitment_list, binding_factors)
diff --git a/spec/frost_spec.rb b/spec/frost_spec.rb
index 06cbd52..f7567a6 100644
--- a/spec/frost_spec.rb
+++ b/spec/frost_spec.rb
@@ -3,6 +3,8 @@
 
 RSpec.describe FROST do
 
+  let(:group) { ECDSA::Group::Secp256k1 }
+
   shared_examples "Test Vector" do
     it do
       # key generation
@@ -112,14 +114,12 @@
 
   describe "Test Vector" do
     context "secp256k1" do
-      let(:group) { ECDSA::Group::Secp256k1 }
       let(:vectors) { load_fixture("secp256k1/vectors.json") }
       it_behaves_like "Test Vector", "secp256k1"
       it_behaves_like "frost process", "secp256k1"
     end
 
     context "secp256k1 big identifiers" do
-      let(:group) { ECDSA::Group::Secp256k1 }
       let(:vectors) { load_fixture("secp256k1/vectors-big-identifier.json") }
       it_behaves_like "Test Vector", "secp256k1 with big identifier"
     end
@@ -138,4 +138,19 @@
     end
   end
 
+  describe "#aggregate" do
+    context "with long commitment list" do
+      it do
+        secret = FROST::SigningKey.generate(group)
+        group_pubkey = secret.to_point
+        comm1 = FROST::Commitments.new(1, group_pubkey, group_pubkey) # fake commitments
+        comm2 = FROST::Commitments.new(2, group_pubkey, group_pubkey) # fake commitments
+        comm3 = FROST::Commitments.new(3, group_pubkey, group_pubkey) # fake commitments
+        msg = ""
+        sig_shares = [1, 2]
+        expect{ described_class.aggregate([comm1, comm2, comm3], msg, group_pubkey, sig_shares) }.
+          to raise_error("The numbers of commitment_list and sig_shares do not match.")
+      end
+    end
+  end
 end