diff --git a/psopacket/src/lib.rs b/psopacket/src/lib.rs
index 48f10c1..c89fb31 100644
--- a/psopacket/src/lib.rs
+++ b/psopacket/src/lib.rs
@@ -374,26 +374,18 @@ pub fn pso_packet(attr: TokenStream, item: TokenStream) -> TokenStream {
     };
 
     if manual_flag {
-        let mut found_flag = false;
-        for attr in attrs.iter() {
-            match attr {
-                AttrType::Array(_, ident, _, _) => {
-                    if ident.to_string() == "flag" {
-                        found_flag = true;
-                        break;
-                    }
-                },
-                AttrType::Value(_, ident, _) => {
-                    if ident.to_string() == "flag" {
-                        found_flag = true;
-                        break;
-                    }
+        match &attrs[0] {
+            AttrType::Array(_, ident, _, _) => {
+                if ident.to_string() != "flag" {
+                    return syn::Error::new(pkt_struct.ident.span(), "struct must have flag as the first field if manual_flag is set").to_compile_error().into();
+                }
+            },
+            AttrType::Value(_, ident, _) => {
+                if ident.to_string() != "flag" {
+                    return syn::Error::new(pkt_struct.ident.span(), "struct must have flag as the first field if manual_flag is set").to_compile_error().into();
                 }
             }
         }
-        if !found_flag {
-            return syn::Error::new(pkt_struct.ident.span(), "struct must have flag if manual_flag is set").to_compile_error().into();
-        }
     }
 
     let struct_def = generate_struct_def(pkt_struct.ident.clone(), &attrs);