diff --git a/o1vm/src/interpreters/mips/tests_helpers.rs b/o1vm/src/interpreters/mips/tests_helpers.rs
index 3840975968..c97b81501c 100644
--- a/o1vm/src/interpreters/mips/tests_helpers.rs
+++ b/o1vm/src/interpreters/mips/tests_helpers.rs
@@ -95,6 +95,7 @@ where
         lookup_multiplicities: LookupMultiplicities::new(),
         lookup_state_idx: 0,
         lookup_state: vec![],
+        lookup_arity: vec![],
         selector: crate::interpreters::mips::column::N_MIPS_SEL_COLS,
         halt: false,
         // Keccak related
diff --git a/o1vm/src/interpreters/mips/witness.rs b/o1vm/src/interpreters/mips/witness.rs
index 3b61250b8a..1c01532bb6 100644
--- a/o1vm/src/interpreters/mips/witness.rs
+++ b/o1vm/src/interpreters/mips/witness.rs
@@ -115,6 +115,10 @@ pub struct Env<Fp, PreImageOracle: PreImageOracleT> {
     pub scratch_state_inverse: [Fp; SCRATCH_SIZE_INVERSE],
     pub lookup_state_idx: usize,
     pub lookup_state: Vec<Fp>,
+    // tracks the arity of every lookup
+    // [1,1,3] means that the lookup state is of size 5,
+    // containing two lookup of arity one and one of arity three.
+    pub lookup_arity: Vec<usize>,
     pub halt: bool,
     pub syscall_env: SyscallEnv,
     pub selector: usize,
@@ -178,9 +182,11 @@ impl<Fp: PrimeField, PreImageOracle: PreImageOracleT> InterpreterEnv for Env<Fp,
     }
 
     fn add_lookup(&mut self, lookup: Lookup<Self::Variable>) {
+        let mut arity_counter = 0;
         let mut add_value = |x: Fp| {
             self.lookup_state_idx += 1;
             self.lookup_state.push(x);
+            arity_counter += 1;
         };
         let Lookup {
             table_id,
@@ -201,7 +207,7 @@ impl<Fp: PrimeField, PreImageOracle: PreImageOracleT> InterpreterEnv for Env<Fp,
         for value in values.iter() {
             add_value(*value);
         }
-
+        // Update multiplicities
         if let Some(idx) = table_id.ix_by_value(values.as_slice()) {
             match table_id {
                 LookupTableIDs::PadLookup => self.lookup_multiplicities.pad_lookup[idx] += 1,
@@ -224,6 +230,8 @@ impl<Fp: PrimeField, PreImageOracle: PreImageOracleT> InterpreterEnv for Env<Fp,
                 LookupTableIDs::KeccakStepLookup => (),
             }
         }
+        //Update arity
+        self.lookup_arity.push(arity_counter);
     }
 
     fn instruction_counter(&self) -> Self::Variable {
@@ -963,6 +971,7 @@ impl<Fp: PrimeField, PreImageOracle: PreImageOracleT> Env<Fp, PreImageOracle> {
             scratch_state_inverse: fresh_scratch_state(),
             lookup_state_idx: 0,
             lookup_state: vec![],
+            lookup_arity: vec![],
             halt: state.exited,
             syscall_env,
             selector,