diff --git a/perlmod-macro/src/function.rs b/perlmod-macro/src/function.rs
index f3069ef..763200c 100644
--- a/perlmod-macro/src/function.rs
+++ b/perlmod-macro/src/function.rs
@@ -1,6 +1,6 @@
 use failure::Error;
 
-use proc_macro2::{Ident, TokenStream};
+use proc_macro2::{Ident, TokenStream, Span};
 
 use quote::quote;
 
@@ -94,6 +94,11 @@ pub fn handle_function(attr: FunctionAttrs, func: syn::ItemFn) -> Result<XSub, E
         }
     }
 
+    let too_many_args_error = syn::LitStr::new(
+        &format!("too many parameters for function '{}', (expected {})", name, sig.inputs.len()),
+        Span::call_site(),
+    );
+
     let tokens = quote! {
         #func
 
@@ -116,6 +121,12 @@ pub fn handle_function(attr: FunctionAttrs, func: syn::ItemFn) -> Result<XSub, E
 
             #extract_arguments
 
+            if args.next().is_some() {
+                return Err(::perlmod::Value::new_string(#too_many_args_error)
+                    .into_mortal()
+                    .into_raw());
+            }
+
             drop(args);
 
             #deserialized_arguments