diff --git a/crates/cli/src/utils/mod.rs b/crates/cli/src/utils/mod.rs
index f833924f57fe..9f8475f63dab 100644
--- a/crates/cli/src/utils/mod.rs
+++ b/crates/cli/src/utils/mod.rs
@@ -39,8 +39,6 @@ pub const STATIC_FUZZ_SEED: [u8; 32] = [
     0x5d, 0x64, 0x0b, 0x19, 0xad, 0xf0, 0xe3, 0x57, 0xb8, 0xd4, 0xbe, 0x7d, 0x49, 0xee, 0x70, 0xe6,
 ];
 
-const DEFAULT_USER_AGENT: &str = concat!("foundry/", env!("CARGO_PKG_VERSION"));
-
 /// Useful extensions to [`std::path::Path`].
 pub trait FoundryPathExt {
     /// Returns true if the [`Path`] ends with `.t.sol`
@@ -112,11 +110,7 @@ pub fn get_provider_builder(config: &Config) -> Result<ProviderBuilder> {
         builder = builder.timeout(Duration::from_secs(rpc_timeout));
     }
 
-    if let Some(mut rpc_headers) = config.eth_rpc_headers.clone() {
-        if !rpc_headers.iter().any(|h| h.starts_with("User-Agent:")) {
-            rpc_headers.push(format!("User-Agent:{DEFAULT_USER_AGENT}"));
-        }
-
+    if let Some(rpc_headers) = config.eth_rpc_headers.clone() {
         builder = builder.headers(rpc_headers);
     }
 
diff --git a/crates/common/src/constants.rs b/crates/common/src/constants.rs
index 0ba0514c2b87..4ff3eb8d70fb 100644
--- a/crates/common/src/constants.rs
+++ b/crates/common/src/constants.rs
@@ -40,6 +40,9 @@ pub const OPTIMISM_SYSTEM_ADDRESS: Address = address!("deaddeaddeaddeaddeaddeadd
 /// Transaction identifier of System transaction types
 pub const SYSTEM_TRANSACTION_TYPE: u8 = 126;
 
+/// Default user agent set as the header for requests that don't specify one.
+pub const DEFAULT_USER_AGENT: &str = concat!("foundry/", env!("CARGO_PKG_VERSION"));
+
 /// Returns whether the sender is a known L2 system sender that is the first tx in every block.
 ///
 /// Transactions from these senders usually don't have a any fee information.
diff --git a/crates/common/src/provider/runtime_transport.rs b/crates/common/src/provider/runtime_transport.rs
index a95969be5a40..563cec313850 100644
--- a/crates/common/src/provider/runtime_transport.rs
+++ b/crates/common/src/provider/runtime_transport.rs
@@ -1,7 +1,7 @@
 //! Runtime transport that connects on first request, which can take either of an HTTP,
 //! WebSocket, or IPC transport and supports retries based on CUPS logic.
 
-use crate::REQUEST_TIMEOUT;
+use crate::{DEFAULT_USER_AGENT, REQUEST_TIMEOUT};
 use alloy_json_rpc::{RequestPacket, ResponsePacket};
 use alloy_pubsub::{PubSubConnect, PubSubFrontend};
 use alloy_rpc_types::engine::{Claims, JwtSecret};
@@ -176,6 +176,14 @@ impl RuntimeTransport {
             );
         }
 
+        if !headers.iter().any(|(k, _v)| k.as_str().starts_with("User-Agent:")) {
+            headers.insert(
+                reqwest::header::USER_AGENT,
+                HeaderValue::from_str(DEFAULT_USER_AGENT)
+                    .expect("User-Agent should be valid string"),
+            );
+        }
+
         client_builder = client_builder.default_headers(headers);
 
         let client =