diff --git a/psopacket/src/lib.rs b/psopacket/src/lib.rs
index 60c7459..48f10c1 100644
--- a/psopacket/src/lib.rs
+++ b/psopacket/src/lib.rs
@@ -342,6 +342,7 @@ pub fn pso_packet(attr: TokenStream, item: TokenStream) -> TokenStream {
     let args = parse_macro_input!(attr as syn::AttributeArgs);
     let mut cmd = 0;
     let mut flag = true;
+    let mut manual_flag = false;
     for a in args {
         match &a {
             NestedMeta::Lit(lit) => {
@@ -353,6 +354,10 @@ pub fn pso_packet(attr: TokenStream, item: TokenStream) -> TokenStream {
                 if let syn::Meta::Path(syn::Path {segments, ..}) = k {
                     match segments[0].ident.to_string().as_str() {
                         "no_flag" => flag = false,
+                        "manual_flag" => {
+                            flag = false;
+                            manual_flag = true;
+                        },
                         _ => {
                             return syn::Error::new(segments[0].ident.span(), "unknown macro param").to_compile_error().into();
                         }
@@ -368,6 +373,29 @@ pub fn pso_packet(attr: TokenStream, item: TokenStream) -> TokenStream {
         Err(err) => return err
     };
 
+    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;
+                    }
+                }
+            }
+        }
+        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);
     let psopacket_impl = generate_psopacket_impl(cmd, pkt_struct.ident.clone(), &attrs, flag);
     let debug_impl =  generate_debug_impl(pkt_struct.ident.clone(), &attrs);