diff --git a/crates/precompile/src/blake2.rs b/crates/precompile/src/blake2.rs
index 1b4ab9256a..6ecf55bebe 100644
--- a/crates/precompile/src/blake2.rs
+++ b/crates/precompile/src/blake2.rs
@@ -17,12 +17,6 @@ pub fn run(input: &Bytes, gas_limit: u64) -> PrecompileResult {
         return Err(Error::Blake2WrongLength.into());
     }
 
-    let f = match input[212] {
-        1 => true,
-        0 => false,
-        _ => return Err(Error::Blake2WrongFinalIndicatorFlag.into()),
-    };
-
     // rounds 4 bytes
     let rounds = u32::from_be_bytes(input[..4].try_into().unwrap()) as usize;
     let gas_used = rounds as u64 * F_ROUND;
@@ -30,6 +24,12 @@ pub fn run(input: &Bytes, gas_limit: u64) -> PrecompileResult {
         return Err(Error::OutOfGas.into());
     }
 
+    let f = match input[212] {
+        1 => true,
+        0 => false,
+        _ => return Err(Error::Blake2WrongFinalIndicatorFlag.into()),
+    };
+
     let mut h = [0u64; 8];
     let mut m = [0u64; 16];