diff --git a/src/lib/types.rs b/src/lib/types.rs
index 68ae842..5e98e95 100644
--- a/src/lib/types.rs
+++ b/src/lib/types.rs
@@ -224,9 +224,7 @@ impl From<Message> for WebcryptRequest {
 impl From<&[u8]> for WebcryptRequest {
     fn from(arr: &[u8]) -> Self {
         let mut wc_magic_number = [0u8; 4]; // FIXME correct that
-        for i in 0..4 {
-            wc_magic_number[i] = arr[1 + i];
-        }
+        wc_magic_number[..4].copy_from_slice(&arr[1..(4 + 1)]);
 
         let mut w = WebcryptRequest {
             operation_webcrypt_constant: arr[0],