diff --git a/src/interpret.ml b/src/interpret.ml
index f4d35669aea..4bafb9875b9 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -699,16 +699,25 @@ and interpret_func env name pat f v (k : V.value V.cont) =
 
 (* Programs *)
 
-let interpret_prog scope p : V.value option * scope =
-  let env = env_of_scope scope in
-  trace_depth := 0;
-  let vo = ref None in
-  let ve = ref V.Env.empty in
-  Scheduler.queue (fun () ->
-    interpret_block env p.it (Some ve) (fun v -> vo := Some v)
-  );
-  Scheduler.run ();
-  !vo, { val_env = !ve; lib_env = scope.lib_env }
+let interpret_prog scope p : (V.value * scope) option =
+  try
+    let env = env_of_scope scope in
+    trace_depth := 0;
+    let vo = ref None in
+    let ve = ref V.Env.empty in
+    Scheduler.queue (fun () ->
+      interpret_block env p.it (Some ve) (fun v -> vo := Some v)
+    );
+    Scheduler.run ();
+    let scope = { val_env = !ve; lib_env = scope.lib_env } in
+    match !vo with
+    | Some v -> Some (v, scope)
+    | None -> None
+  with exn ->
+    (* For debugging, should never happen. *)
+    print_exn exn;
+    None
+
 
 let interpret_library scope (filename, p) : scope =
   let env = env_of_scope scope in
diff --git a/src/interpret.mli b/src/interpret.mli
index e7352bbe5ef..6f18c5d3859 100644
--- a/src/interpret.mli
+++ b/src/interpret.mli
@@ -11,7 +11,5 @@ val adjoin_scope : scope -> scope -> scope
 
 exception Trap of Source.region * string
 
-val interpret_prog : scope -> Syntax.prog -> V.value option * scope
+val interpret_prog : scope -> Syntax.prog -> (V.value * scope) option
 val interpret_library : scope -> Syntax.library -> scope
-
-val print_exn : exn -> unit
diff --git a/src/interpret_ir.ml b/src/interpret_ir.ml
index 95e4dfa4774..85f2d7b860a 100644
--- a/src/interpret_ir.ml
+++ b/src/interpret_ir.ml
@@ -653,8 +653,11 @@ let interpret_prog scope ((ds, exp), _flavor) : scope =
   let env = env_of_scope scope in
   trace_depth := 0;
   let ve = ref V.Env.empty in
-  Scheduler.queue (fun () ->
-    interpret_block env (Some ve) ds exp  (fun v -> ())
-  );
-  Scheduler.run ();
-  !ve
+  try
+    Scheduler.queue (fun () ->
+      interpret_block env (Some ve) ds exp  (fun v -> ())
+    );
+    Scheduler.run ();
+    !ve
+  with exn -> print_exn exn; !ve
+
diff --git a/src/interpret_ir.mli b/src/interpret_ir.mli
index e9d969d65b8..4dea591faaa 100644
--- a/src/interpret_ir.mli
+++ b/src/interpret_ir.mli
@@ -9,5 +9,3 @@ val adjoin_scope : scope -> scope -> scope
 exception Trap of Source.region * string
 
 val interpret_prog : scope -> Ir.prog -> scope
-
-val print_exn : exn -> unit
diff --git a/src/main.ml b/src/main.ml
index 66ac27479b8..b5ae9b634da 100644
--- a/src/main.ml
+++ b/src/main.ml
@@ -105,9 +105,6 @@ let () =
   (useful for debugging infinite loops)
   *)
   Printexc.record_backtrace true;
-  try
-    Arg.parse argspec add_arg usage;
-    if !mode = Default then mode := (if !args = [] then Interact else Compile);
-    process_files !args
-  with exn ->
-    Interpret.print_exn exn
+  Arg.parse argspec add_arg usage;
+  if !mode = Default then mode := (if !args = [] then Interact else Compile);
+  process_files !args
diff --git a/src/pipeline.ml b/src/pipeline.ml
index 41bafd3e44d..bda5cdb204d 100644
--- a/src/pipeline.ml
+++ b/src/pipeline.ml
@@ -224,15 +224,8 @@ let load_decl parse_one senv : load_decl_result =
 (* Interpretation (Source) *)
 
 let interpret_prog denv prog : (Value.value * Interpret.scope) option =
-  try
-    phase "Interpreting" prog.Source.note;
-    match Interpret.interpret_prog denv prog with
-    | None, _ -> None
-    | Some v, scope -> Some (v, scope)
-  with exn ->
-    (* For debugging, should never happen. *)
-    Interpret.print_exn exn;
-    None
+  phase "Interpreting" prog.Source.note;
+  Interpret.interpret_prog denv prog
 
 let rec interpret_libraries denv libraries : Interpret.scope =
   match libraries with
diff --git a/test/fail/ok/ast81-clash.tc.ok b/test/fail/ok/ast81-clash.tc.ok
index a44cd01d45f..d24e7265597 100644
--- a/test/fail/ok/ast81-clash.tc.ok
+++ b/test/fail/ok/ast81-clash.tc.ok
@@ -1,63 +1 @@
-prelude:189.1-214.2: internal error, Env.Make(X).Clash("x")
-
-Last environment:
-@new_async = func
-@text_of_Bool = func
-@text_of_Int = func
-@text_of_Nat = func
-@text_of_Text = func
-@text_of_array = func
-@text_of_array_mut = func
-@text_of_option = func
-@text_of_variant = func
-Array_init = func
-Array_tabulate = func
-abs = func
-btstWord16 = func
-btstWord32 = func
-btstWord64 = func
-btstWord8 = func
-charToText = func
-charToWord32 = func
-clzWord16 = func
-clzWord32 = func
-clzWord64 = func
-clzWord8 = func
-ctzWord16 = func
-ctzWord32 = func
-ctzWord64 = func
-ctzWord8 = func
-decodeUTF8 = func
-hashInt = func
-ignore = func
-intToWord16 = func
-intToWord32 = func
-intToWord64 = func
-intToWord8 = func
-natToWord16 = func
-natToWord32 = func
-natToWord64 = func
-natToWord8 = func
-popcntWord16 = func
-popcntWord32 = func
-popcntWord64 = func
-popcntWord8 = func
-print = func
-printChar = func
-printInt = func
-range = func
-revrange = func
-shrsWord16 = func
-shrsWord32 = func
-shrsWord64 = func
-shrsWord8 = func
-word16ToInt = func
-word16ToNat = func
-word32ToChar = func
-word32ToInt = func
-word32ToNat = func
-word64ToInt = func
-word64ToNat = func
-word8ToInt = func
-word8ToNat = func
-
+Fatal error: exception Env.Make(X).Clash("x")