diff --git a/crates/config/src/lib.rs b/crates/config/src/lib.rs
index 9f7ed16e79106..0c4cecfddce97 100644
--- a/crates/config/src/lib.rs
+++ b/crates/config/src/lib.rs
@@ -345,7 +345,8 @@ pub struct Config {
     /// the initial balance of each deployed test contract
     pub initial_balance: U256,
     /// the block.number value during EVM execution
-    pub block_number: u64,
+    #[serde(deserialize_with = "crate::deser_u64_to_u256")]
+    pub block_number: U256,
     /// pins the block number for the state fork
     pub fork_block_number: Option<u64>,
     /// The chain name or EIP-155 chain ID.
@@ -365,7 +366,8 @@ pub struct Config {
     /// The `block.coinbase` value during EVM execution.
     pub block_coinbase: Address,
     /// The `block.timestamp` value during EVM execution.
-    pub block_timestamp: u64,
+    #[serde(deserialize_with = "crate::deser_u64_to_u256")]
+    pub block_timestamp: U256,
     /// The `block.difficulty` value during EVM execution.
     pub block_difficulty: u64,
     /// Before merge the `block.max_hash`, after merge it is `block.prevrandao`.
@@ -1660,8 +1662,8 @@ impl Config {
     pub fn dapptools() -> Self {
         Self {
             chain: Some(Chain::from_id(99)),
-            block_timestamp: 0,
-            block_number: 0,
+            block_timestamp: U256::ZERO,
+            block_number: U256::ZERO,
             ..Self::default()
         }
     }
@@ -2352,7 +2354,7 @@ impl Default for Config {
             sender: Self::DEFAULT_SENDER,
             tx_origin: Self::DEFAULT_SENDER,
             initial_balance: U256::from((1u128 << 96) - 1),
-            block_number: 1,
+            block_number: U256::from(1),
             fork_block_number: None,
             chain: None,
             gas_limit: (1u64 << 30).into(), // ~1B
@@ -2360,7 +2362,7 @@ impl Default for Config {
             gas_price: None,
             block_base_fee_per_gas: 0,
             block_coinbase: Address::ZERO,
-            block_timestamp: 1,
+            block_timestamp: U256::from(1),
             block_difficulty: 0,
             block_prevrandao: Default::default(),
             block_gas_limit: None,
diff --git a/crates/config/src/utils.rs b/crates/config/src/utils.rs
index bcb20ab698afb..39b6e6c88a0d3 100644
--- a/crates/config/src/utils.rs
+++ b/crates/config/src/utils.rs
@@ -213,6 +213,24 @@ where
     deserialize_u64_or_max(deserializer)?.try_into().map_err(D::Error::custom)
 }
 
+/// Deserialize into `U256` from either a `u64` or a `U256` hex string.
+pub fn deser_u64_to_u256<'de, D>(deserializer: D) -> Result<U256, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    enum NumericValue {
+        U256(U256),
+        U64(u64),
+    }
+
+    match NumericValue::deserialize(deserializer)? {
+        NumericValue::U64(n) => Ok(U256::from(n)),
+        NumericValue::U256(n) => Ok(n),
+    }
+}
+
 /// Helper type to parse both `u64` and `U256`
 #[derive(Clone, Copy, Deserialize)]
 #[serde(untagged)]
diff --git a/crates/evm/core/src/opts.rs b/crates/evm/core/src/opts.rs
index ee20d7f55c69c..aa06eea4f35ac 100644
--- a/crates/evm/core/src/opts.rs
+++ b/crates/evm/core/src/opts.rs
@@ -278,9 +278,11 @@ pub struct Env {
     pub block_coinbase: Address,
 
     /// the block.timestamp value during EVM execution
+    #[serde(deserialize_with = "foundry_config::deser_u64_to_u256")]
     pub block_timestamp: U256,
 
     /// the block.number value during EVM execution"
+    #[serde(deserialize_with = "foundry_config::deser_u64_to_u256")]
     pub block_number: U256,
 
     /// the block.difficulty value during EVM execution
diff --git a/crates/forge/tests/cli/config.rs b/crates/forge/tests/cli/config.rs
index 05f1b78340157..2063646778fd4 100644
--- a/crates/forge/tests/cli/config.rs
+++ b/crates/forge/tests/cli/config.rs
@@ -101,7 +101,7 @@ forgetest!(can_extract_config_values, |prj, cmd| {
         sender: "00a329c0648769A73afAc7F9381D08FB43dBEA72".parse().unwrap(),
         tx_origin: "00a329c0648769A73afAc7F9F81E08FB43dBEA72".parse().unwrap(),
         initial_balance: U256::from(0xffffffffffffffffffffffffu128),
-        block_number: 10,
+        block_number: U256::from(10),
         fork_block_number: Some(200),
         chain: Some(9999.into()),
         gas_limit: 99_000_000u64.into(),
@@ -109,7 +109,7 @@ forgetest!(can_extract_config_values, |prj, cmd| {
         gas_price: Some(999),
         block_base_fee_per_gas: 10,
         block_coinbase: Address::random(),
-        block_timestamp: 10,
+        block_timestamp: U256::from(10),
         block_difficulty: 10,
         block_prevrandao: B256::random(),
         block_gas_limit: Some(100u64.into()),
diff --git a/crates/forge/tests/it/test_helpers.rs b/crates/forge/tests/it/test_helpers.rs
index 22e6df8724ed7..2209fb9409230 100644
--- a/crates/forge/tests/it/test_helpers.rs
+++ b/crates/forge/tests/it/test_helpers.rs
@@ -100,8 +100,8 @@ impl ForgeTestProfile {
         config.gas_limit = u64::MAX.into();
         config.chain = None;
         config.tx_origin = CALLER;
-        config.block_number = 1;
-        config.block_timestamp = 1;
+        config.block_number = U256::from(1);
+        config.block_timestamp = U256::from(1);
 
         config.sender = CALLER;
         config.initial_balance = U256::MAX;