diff --git a/src/cat/cat.rs b/src/cat/cat.rs
index c1a81bf05..90db91ee8 100644
--- a/src/cat/cat.rs
+++ b/src/cat/cat.rs
@@ -320,6 +320,9 @@ impl<'a, W: Write> UnsafeWriter<'a, W> {
     }
 }
 
+// This method was used in Write::write only. It must not be called in the correct cat code
+// and is placed in the bottleneck place, so it is not used anymore. 
+// Uncomment this and code in Write::write for more convenient testing of a new cat version.
 //#[inline(never)]
 //fn fail() -> ! {
 //    panic!("assertion failed");
@@ -329,8 +332,8 @@ impl<'a, W: Write> Write for UnsafeWriter<'a, W> {
     fn write(&mut self, buf: &[u8]) -> Result<usize> {
         //let dst = &mut self.buf[self.pos..];
         let len = buf.len();
-        // assertion is  true for current code
-        // and it is a bottlneck place
+        // the condition is false for current code and every correct code
+        // see fail method comment for more information
         // if len > dst.len() {
         //     fail();
         // }