diff --git a/.changes/fixed/3187.md b/.changes/fixed/3187.md
new file mode 100644
index 00000000000..02db15c563c
--- /dev/null
+++ b/.changes/fixed/3187.md
@@ -0,0 +1 @@
+Use `String` for block type in GraphQL response extensions
\ No newline at end of file
diff --git a/crates/client/src/reqwest_ext.rs b/crates/client/src/reqwest_ext.rs
index 100dd4da8f7..9341806231c 100644
--- a/crates/client/src/reqwest_ext.rs
+++ b/crates/client/src/reqwest_ext.rs
@@ -10,10 +10,18 @@ use fuel_core_types::{
     },
     fuel_types::BlockHeight,
 };
+use serde::{
+    Deserialize,
+    de::{
+        self,
+        Deserializer,
+    },
+};
 use std::{
     future::Future,
     marker::PhantomData,
     pin::Pin,
+    str::FromStr,
 };
 
 #[derive(Debug, Clone, serde::Serialize)]
@@ -24,6 +32,7 @@ pub struct ExtensionsRequest {
 #[derive(Debug, Clone, serde::Deserialize)]
 pub struct ExtensionsResponse {
     pub required_fuel_block_height: Option<BlockHeight>,
+    #[serde(default, deserialize_with = "deserialize_block_height_option")]
     pub current_fuel_block_height: Option<BlockHeight>,
     pub fuel_block_height_precondition_failed: Option<bool>,
     pub current_stf_version: Option<StateTransitionBytecodeVersion>,
@@ -58,6 +67,22 @@ impl<Operation> FuelOperation<Operation> {
     }
 }
 
+fn deserialize_block_height_option<'de, D>(
+    deserializer: D,
+) -> Result<Option<BlockHeight>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let value = Option::<String>::deserialize(deserializer)?;
+    match value {
+        None => Ok(None),
+        Some(value) => {
+            let height = BlockHeight::from_str(&value).map_err(de::Error::custom)?;
+            Ok(Some(height))
+        }
+    }
+}
+
 #[cfg(not(target_arch = "wasm32"))]
 type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;
 
diff --git a/crates/fuel-core/src/graphql_api/extensions/chain_state_info.rs b/crates/fuel-core/src/graphql_api/extensions/chain_state_info.rs
index 967635992a3..d41436ab923 100644
--- a/crates/fuel-core/src/graphql_api/extensions/chain_state_info.rs
+++ b/crates/fuel-core/src/graphql_api/extensions/chain_state_info.rs
@@ -118,11 +118,8 @@ fn set_current_state<E>(
         Value::Number(current_stf_version.into()),
     );
 
-    let current_block_height: u32 = *current_block_height;
-    extensions.set(
-        CURRENT_FUEL_BLOCK_HEIGHT,
-        Value::Number(current_block_height.into()),
-    );
+    let block_height_str = block_to_trimmed_string(current_block_height);
+    extensions.set(CURRENT_FUEL_BLOCK_HEIGHT, Value::String(block_height_str));
 }
 
 trait SetExtensionsResponse {
@@ -141,6 +138,21 @@ impl SetExtensionsResponse for BTreeMap<String, Value> {
     }
 }
 
+fn block_to_trimmed_string(block_height: BlockHeight) -> String {
+    let mut block_height_str = block_height.to_string();
+
+    // trim leading zeros
+    let cut = block_height_str
+        .as_bytes()
+        .iter()
+        .position(|&b| b != b'0')
+        // if it's all zeros, keep a single "0"
+        .unwrap_or(block_height_str.len().saturating_sub(1));
+
+    block_height_str.drain(..cut);
+    block_height_str
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;