diff --git a/src/syscall/mod.rs b/src/syscall/mod.rs
index 7233c8d8a0..b2f93d8e4f 100644
--- a/src/syscall/mod.rs
+++ b/src/syscall/mod.rs
@@ -276,7 +276,10 @@ pub fn syscall(
             SYS_MPROTECT => mprotect(b, c, MapFlags::from_bits_truncate(d), token).map(|()| 0),
             SYS_MREMAP => mremap(b, c, d, e, f, token),
 
-            _ => Err(Error::new(ENOSYS)),
+            _ => {
+                println!("KERNEL: unimplemented syscall a={:#x} b={:#x} c={:#x} d={:#x}", a, b, c, d);
+                Err(Error::new(ENOSYS))
+            }
         }
     }