diff --git a/Cargo.lock b/Cargo.lock
index c09ebf212b..8e7a4c094c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1082,6 +1082,7 @@ dependencies = [
  "eyre",
  "goblin",
  "hex",
+ "num-bigint-dig",
  "openvm-build",
  "openvm-circuit",
  "openvm-cli-example-test",
diff --git a/book/src/custom-extensions/algebra.md b/book/src/custom-extensions/algebra.md
index c9a6b32f95..b5b00aea3e 100644
--- a/book/src/custom-extensions/algebra.md
+++ b/book/src/custom-extensions/algebra.md
@@ -141,3 +141,17 @@ pub fn main() {
     // Note that these assertions would fail, have we provided the `mod_idx` parameters wrongly.
 }
 ```
+
+### Config parameters
+
+For the guest program to build successfully, all used moduli must be declared in the `.toml` config file in the following format:
+
+```toml
+[app_vm_config.modular]
+supported_modulus = ["115792089237316195423570985008687907853269984665640564039457584007908834671663"]
+
+[app_vm_config.fp2]
+supported_modulus = ["115792089237316195423570985008687907853269984665640564039457584007908834671663"]
+```
+
+The `supported_modulus` parameter is a list of moduli that the guest program will use. They must be provided in decimal format in the `.toml` file.
\ No newline at end of file
diff --git a/crates/cli/Cargo.toml b/crates/cli/Cargo.toml
index 759bb9624d..b780ff724f 100644
--- a/crates/cli/Cargo.toml
+++ b/crates/cli/Cargo.toml
@@ -47,6 +47,7 @@ prettytable-rs = "0.10"
 textwrap = "0.16.0"
 ctrlc = "3.4.2"
 toml = { workspace = true }
+num-bigint-dig = { workspace = true, features = ["serde"] }
 
 [dev-dependencies]
 openvm-cli-example-test = { path = "example" }
diff --git a/extensions/algebra/circuit/src/fp2_extension.rs b/extensions/algebra/circuit/src/fp2_extension.rs
index f6276f0c4f..8942c47867 100644
--- a/extensions/algebra/circuit/src/fp2_extension.rs
+++ b/extensions/algebra/circuit/src/fp2_extension.rs
@@ -19,10 +19,14 @@ use openvm_stark_backend::p3_field::PrimeField32;
 use serde::{Deserialize, Serialize};
 use strum::EnumCount;
 
-use crate::fp2_chip::{Fp2AddSubChip, Fp2MulDivChip};
+use crate::{
+    fp2_chip::{Fp2AddSubChip, Fp2MulDivChip},
+    util::deserialize_vec_biguint_from_str,
+};
 
 #[derive(Clone, Debug, derive_new::new, Serialize, Deserialize)]
 pub struct Fp2Extension {
+    #[serde(deserialize_with = "deserialize_vec_biguint_from_str")]
     pub supported_modulus: Vec<BigUint>,
 }
 
diff --git a/extensions/algebra/circuit/src/lib.rs b/extensions/algebra/circuit/src/lib.rs
index ffddacc61a..7018513dcf 100644
--- a/extensions/algebra/circuit/src/lib.rs
+++ b/extensions/algebra/circuit/src/lib.rs
@@ -1,6 +1,8 @@
 pub mod fp2_chip;
 pub mod modular_chip;
 
+mod util;
+
 mod fp2;
 pub use fp2::*;
 mod modular_extension;
diff --git a/extensions/algebra/circuit/src/modular_extension.rs b/extensions/algebra/circuit/src/modular_extension.rs
index 604a1ea8e2..ccce43ada0 100644
--- a/extensions/algebra/circuit/src/modular_extension.rs
+++ b/extensions/algebra/circuit/src/modular_extension.rs
@@ -20,13 +20,17 @@ use openvm_stark_backend::p3_field::PrimeField32;
 use serde::{Deserialize, Serialize};
 use strum::EnumCount;
 
-use crate::modular_chip::{
-    ModularAddSubChip, ModularAddSubCoreChip, ModularIsEqualChip, ModularIsEqualCoreChip,
-    ModularMulDivChip, ModularMulDivCoreChip,
+use crate::{
+    modular_chip::{
+        ModularAddSubChip, ModularAddSubCoreChip, ModularIsEqualChip, ModularIsEqualCoreChip,
+        ModularMulDivChip, ModularMulDivCoreChip,
+    },
+    util::deserialize_vec_biguint_from_str,
 };
 
 #[derive(Clone, Debug, derive_new::new, Serialize, Deserialize)]
 pub struct ModularExtension {
+    #[serde(deserialize_with = "deserialize_vec_biguint_from_str")]
     pub supported_modulus: Vec<BigUint>,
 }
 
diff --git a/extensions/algebra/circuit/src/util.rs b/extensions/algebra/circuit/src/util.rs
new file mode 100644
index 0000000000..54bdba4348
--- /dev/null
+++ b/extensions/algebra/circuit/src/util.rs
@@ -0,0 +1,16 @@
+use num_bigint_dig::BigUint;
+use serde::Deserialize;
+
+pub(crate) fn deserialize_vec_biguint_from_str<'de, D>(
+    deserializer: D,
+) -> Result<Vec<BigUint>, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    let v: Vec<String> = Deserialize::deserialize(deserializer)?;
+    let res = v.into_iter().map(|s| s.parse()).collect::<Vec<_>>();
+    if res.iter().any(|x| x.is_err()) {
+        return Err(serde::de::Error::custom("Failed to parse BigUint"));
+    }
+    Ok(res.into_iter().map(|x| x.unwrap()).collect())
+}