diff --git a/rvsol/src/RISCV.sol b/rvsol/src/RISCV.sol
index 1bbb681e..3b190109 100644
--- a/rvsol/src/RISCV.sol
+++ b/rvsol/src/RISCV.sol
@@ -346,6 +346,13 @@ contract RISCV is IBigStepper {
             }
             if iszero(eq(_proof.offset, proofContentOffset())) { revert(0, 0) }
 
+            if mod(calldataload(sub(proofContentOffset(), 32)), mul(60, 32)) {
+                // proof offset must be stateContentOffset+paddedStateSize+32
+                // proof size: 64-5+1=60 * 32 byte leaf,
+                // so the proofSize must be a multiple of 60*32
+                revert(0, 0)
+            }
+
             //
             // State loading
             //
diff --git a/rvsol/test/RISCV.t.sol b/rvsol/test/RISCV.t.sol
index 79849ff4..e62b2455 100644
--- a/rvsol/test/RISCV.t.sol
+++ b/rvsol/test/RISCV.t.sol
@@ -2371,11 +2371,25 @@ contract RISCV_Test is CommonTest {
         riscv.step(encodedState, proof, 0);
     }
 
+    function test_invalid_proof_size() public {
+        uint32 insn = encodeRType(0xff, 0, 0, 0, 0, 0);
+        (State memory state, bytes memory proof) = constructRISCVState(0, insn);
+        bytes memory encodedState = encodeState(state);
+        proof = hex"00"; // Invalid memory proof size
+
+        vm.expectRevert();
+        riscv.step(encodedState, proof, 0);
+    }
+
     function test_invalid_proof() public {
         uint32 insn = encodeRType(0xff, 0, 0, 0, 0, 0);
         (State memory state, bytes memory proof) = constructRISCVState(0, insn);
         bytes memory encodedState = encodeState(state);
-        proof = hex"00"; // Invalid memory proof
+
+        // Overwrite the first 60 bytes of the proof with zero to create invalid memory proof
+        for (uint256 i = 0; i < 60 && i < proof.length; i++) {
+            proof[i] = 0x00;
+        }
 
         vm.expectRevert(hex"00000000000000000000000000000000000000000000000000000000badf00d1");
         riscv.step(encodedState, proof, 0);