diff --git a/src/Engine.ml b/src/Engine.ml
index 360397e4e1f9f934b9cae535056664a78c87201a..89a372d944b82ad095bdb007957f4d1e5f91e1a7 100644
--- a/src/Engine.ml
+++ b/src/Engine.ml
@@ -1392,13 +1392,20 @@ let main_afl source prologue fuel =
 (* [main_random source prologue fuel] performs an unbounded number of test
    runs in random mode. *)
 
-(* We use an explicit infinite loop to perform an unbounded number of runs.
-   The source channel (/dev/urandom) is opened just once, as it would be
-   pointless to close it and reopen it many times. *)
-
-(* We arrange to print information roughly every second. We print how many
-   tests have been performed so far, our overall average speed, and our
-   current speed. *)
+(* While the tests run, we print information roughly every second. We print
+   how many tests have been performed so far, our overall average speed, and
+   our current speed. *)
+
+(* The arguments [prologue] and [fuel] are passed to [run]. If a failure is
+   discovered, the problematic scenario is printed to [stdout] and logged to a
+   file in the directory ./output/crashes. Then, we start over with a possibly
+   smaller value of [fuel], in the hope of discovering a shorter failure
+   scenario. *)
+
+(* For each value of [fuel], we use an explicit infinite loop to perform an
+   unbounded number of runs. The source of random bits, which is specified by
+   the parameter [source], is opened just once, as it would be pointless to
+   close it and reopen it many times. *)
 
 let rec main_random source prologue fuel =
   try