diff --git a/evm/src/cpu/kernel/asm/curve/bn254/curve_arithmetic/glv.asm b/evm/src/cpu/kernel/asm/curve/bn254/curve_arithmetic/glv.asm
index bd903b21..32eb5b6c 100644
--- a/evm/src/cpu/kernel/asm/curve/bn254/curve_arithmetic/glv.asm
+++ b/evm/src/cpu/kernel/asm/curve/bn254/curve_arithmetic/glv.asm
@@ -97,9 +97,9 @@ contd:
 
 underflowed:
     // stack: underflow, k, s*k2, N, k2
-    // Compute (k-s*k2)%N. TODO: Use SUBMOD here when ready
-    %stack (u, k, x, N, k2) -> (N, x, k, N, k2, u)
-    SUB ADDMOD
+    // Compute (k-s*k2)%N.
+    %stack (u, k, x, N, k2) -> (k, x, N, k2, u)
+    SUBMOD
     %stack (k1, k2, underflow, retdest) -> (retdest, underflow, k1, k2)
     JUMP
 
diff --git a/evm/src/cpu/kernel/asm/curve/secp256k1/curve_add.asm b/evm/src/cpu/kernel/asm/curve/secp256k1/curve_add.asm
index 9e416e66..8664b3e2 100644
--- a/evm/src/cpu/kernel/asm/curve/secp256k1/curve_add.asm
+++ b/evm/src/cpu/kernel/asm/curve/secp256k1/curve_add.asm
@@ -208,11 +208,10 @@ global secp_double:
 %endmacro
 
 // Modular subtraction.
-// TODO: Use SUBMOD when it's ready
 %macro submod_secp_base
     // stack: x, y
-    %stack (x, y) -> (@SECP_BASE, y, x, @SECP_BASE)
-    SUB ADDMOD
+    %stack (x, y) -> (x, y, @SECP_BASE)
+    SUBMOD
 %endmacro
 
 // Check if (x,y) is a valid curve point.
diff --git a/evm/src/cpu/kernel/asm/curve/secp256k1/glv.asm b/evm/src/cpu/kernel/asm/curve/secp256k1/glv.asm
index eee0dc63..26d887f2 100644
--- a/evm/src/cpu/kernel/asm/curve/secp256k1/glv.asm
+++ b/evm/src/cpu/kernel/asm/curve/secp256k1/glv.asm
@@ -84,9 +84,9 @@ global secp_glv_decompose:
 
 underflowed:
     // stack: underflow, k, s*k2, N, k2
-    // Compute (k-s*k2)%N. TODO: Use SUBMOD here when ready
-    %stack (u, k, x, N, k2) -> (N, x, k, N, k2, u)
-    SUB ADDMOD
+    // Compute (k-s*k2)%N.
+    %stack (u, k, x, N, k2) -> (k, x, N, k2, u)
+    SUBMOD
     %stack (k1, k2, underflow, retdest) -> (retdest, underflow, k1, k2)
     JUMP
 
diff --git a/evm/src/cpu/kernel/interpreter.rs b/evm/src/cpu/kernel/interpreter.rs
index 315e93f1..4ba6e9dc 100644
--- a/evm/src/cpu/kernel/interpreter.rs
+++ b/evm/src/cpu/kernel/interpreter.rs
@@ -349,6 +349,7 @@ impl<'a> Interpreter<'a> {
             0x0c => self.run_addfp254(),                                // "ADDFP254",
             0x0d => self.run_mulfp254(),                                // "MULFP254",
             0x0e => self.run_subfp254(),                                // "SUBFP254",
+            0x0f => self.run_submod(),                                  // "SUBMOD",
             0x10 => self.run_lt(),                                      // "LT",
             0x11 => self.run_gt(),                                      // "GT",
             0x12 => self.run_slt(),                                     // "SLT",
@@ -583,6 +584,17 @@ impl<'a> Interpreter<'a> {
         });
     }
 
+    fn run_submod(&mut self) {
+        let x = U512::from(self.pop());
+        let y = U512::from(self.pop());
+        let z = U512::from(self.pop());
+        self.push(if z.is_zero() {
+            U256::zero()
+        } else {
+            U256::try_from((z + x - y) % z).unwrap()
+        });
+    }
+
     fn run_mulmod(&mut self) {
         let x = self.pop();
         let y = self.pop();
@@ -1220,6 +1232,7 @@ fn get_mnemonic(opcode: u8) -> &'static str {
         0x0c => "ADDFP254",
         0x0d => "MULFP254",
         0x0e => "SUBFP254",
+        0x0f => "SUBMOD",
         0x10 => "LT",
         0x11 => "GT",
         0x12 => "SLT",
diff --git a/evm/src/cpu/kernel/opcodes.rs b/evm/src/cpu/kernel/opcodes.rs
index 2503a92e..b8732079 100644
--- a/evm/src/cpu/kernel/opcodes.rs
+++ b/evm/src/cpu/kernel/opcodes.rs
@@ -22,6 +22,7 @@ pub fn get_opcode(mnemonic: &str) -> u8 {
         "ADDFP254" => 0x0c,
         "MULFP254" => 0x0d,
         "SUBFP254" => 0x0e,
+        "SUBMOD" => 0x0f,
         "LT" => 0x10,
         "GT" => 0x11,
         "SLT" => 0x12,
diff --git a/evm/src/witness/gas.rs b/evm/src/witness/gas.rs
index aa312078..6f63a979 100644
--- a/evm/src/witness/gas.rs
+++ b/evm/src/witness/gas.rs
@@ -10,6 +10,7 @@ const G_HIGH: u64 = 10;
 
 pub(crate) fn gas_to_charge(op: Operation) -> u64 {
     use crate::arithmetic::BinaryOperator::*;
+    use crate::arithmetic::TernaryOperator::*;
     use crate::witness::operation::Operation::*;
     match op {
         Iszero => G_VERYLOW,
@@ -30,7 +31,9 @@ pub(crate) fn gas_to_charge(op: Operation) -> u64 {
         BinaryArithmetic(AddFp254) => KERNEL_ONLY_INSTR,
         BinaryArithmetic(MulFp254) => KERNEL_ONLY_INSTR,
         BinaryArithmetic(SubFp254) => KERNEL_ONLY_INSTR,
-        TernaryArithmetic(_) => G_MID,
+        TernaryArithmetic(AddMod) => G_MID,
+        TernaryArithmetic(MulMod) => G_MID,
+        TernaryArithmetic(SubMod) => KERNEL_ONLY_INSTR,
         KeccakGeneral => KERNEL_ONLY_INSTR,
         ProverInput => KERNEL_ONLY_INSTR,
         Pop => G_BASE,