diff --git a/.changeset/silent-pugs-scream.md b/.changeset/silent-pugs-scream.md
new file mode 100644
index 00000000000..c92d12486b3
--- /dev/null
+++ b/.changeset/silent-pugs-scream.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': patch
+---
+
+`GovernorCompatibilityBravo`: Fix encoding of proposal data when signatures are missing.
diff --git a/contracts/governance/compatibility/GovernorCompatibilityBravo.sol b/contracts/governance/compatibility/GovernorCompatibilityBravo.sol
index a903ae98de0..997a81097ca 100644
--- a/contracts/governance/compatibility/GovernorCompatibilityBravo.sol
+++ b/contracts/governance/compatibility/GovernorCompatibilityBravo.sol
@@ -69,6 +69,11 @@ abstract contract GovernorCompatibilityBravo is IGovernorTimelock, IGovernorComp
         bytes[] memory calldatas,
         string memory description
     ) public virtual override returns (uint256) {
+        require(signatures.length == calldatas.length, "GovernorBravo: invalid signatures length");
+        // Stores the full proposal and fallback to the public (possibly overridden) propose. The fallback is done
+        // after the full proposal is stored, so the store operation included in the fallback will be skipped. Here we
+        // call `propose` and not `super.propose` to make sure if a child contract override `propose`, whatever code
+        // is added their is also executed when calling this alternative interface.
         _storeProposal(_msgSender(), targets, values, signatures, calldatas, description);
         return propose(targets, values, _encodeCalldata(signatures, calldatas), description);
     }
@@ -124,8 +129,7 @@ abstract contract GovernorCompatibilityBravo is IGovernorTimelock, IGovernorComp
         returns (bytes[] memory)
     {
         bytes[] memory fullcalldatas = new bytes[](calldatas.length);
-
-        for (uint256 i = 0; i < signatures.length; ++i) {
+        for (uint256 i = 0; i < fullcalldatas.length; ++i) {
             fullcalldatas[i] = bytes(signatures[i]).length == 0
                 ? calldatas[i]
                 : abi.encodePacked(bytes4(keccak256(bytes(signatures[i]))), calldatas[i]);
diff --git a/test/governance/compatibility/GovernorCompatibilityBravo.test.js b/test/governance/compatibility/GovernorCompatibilityBravo.test.js
index 79950474cf7..386a7e80ec3 100644
--- a/test/governance/compatibility/GovernorCompatibilityBravo.test.js
+++ b/test/governance/compatibility/GovernorCompatibilityBravo.test.js
@@ -223,6 +223,21 @@ contract('GovernorCompatibilityBravo', function (accounts) {
     );
   });
 
+  it('with inconsistent array size for selector and arguments', async function () {
+    const target = this.receiver.address;
+    this.helper.setProposal(
+      {
+        targets: [target, target],
+        values: [0, 0],
+        signatures: ['mockFunction()'], // One signature
+        data: ['0x', this.receiver.contract.methods.mockFunctionWithArgs(17, 42).encodeABI()], // Two data entries
+      },
+      '<proposal description>',
+    );
+
+    await expectRevert(this.helper.propose({ from: proposer }), 'GovernorBravo: invalid signatures length');
+  });
+
   describe('should revert', function () {
     describe('on propose', function () {
       it('if proposal does not meet proposalThreshold', async function () {