diff --git a/syntax/check.rs b/syntax/check.rs
index 0c75de8..a90db49 100644
--- a/syntax/check.rs
+++ b/syntax/check.rs
@@ -230,6 +230,11 @@
                 );
             }
         }
+        if let Type::Ref(ity) = &arg.ty {
+            if let Type::Ref(_) = &ity.inner {
+                cx.error(arg, "Passing a reference to a reference is not supported");
+            }
+        }
     }
 
     if let Some(ty) = &efn.ret {