diff --git a/core/compiler/tests/stack-trace.factor b/core/compiler/tests/stack-trace.factor
index 3b1a5c6c85..1085feb0c6 100755
--- a/core/compiler/tests/stack-trace.factor
+++ b/core/compiler/tests/stack-trace.factor
@@ -30,10 +30,3 @@ words splitting grouping sorting ;
     \ + stack-trace-contains?
     \ > stack-trace-contains?
 ] unit-test
-
-: quux ( -- seq ) { 1 2 3 } [ "hi" throw ] sort ;
-
-[ t ] [
-    [ 10 quux ] ignore-errors
-    \ sort stack-trace-contains?
-] unit-test
diff --git a/core/optimizer/optimizer-tests.factor b/core/optimizer/optimizer-tests.factor
index ab808d7914..1e659f1b99 100755
--- a/core/optimizer/optimizer-tests.factor
+++ b/core/optimizer/optimizer-tests.factor
@@ -219,7 +219,7 @@ M: number detect-number ;
 
 ! Regression
 USE: sorting
-USE: sorting.private
+USE: binary-search.private
 
 : old-binsearch ( elt quot seq -- elt quot i )
     dup length 1 <= [
@@ -227,7 +227,7 @@ USE: sorting.private
     ] [
         [ midpoint swap call ] 3keep roll dup zero?
         [ drop dup slice-from swap midpoint@ + ]
-        [ partition old-binsearch ] if
+        [ dup midpoint@ cut-slice old-binsearch ] if
     ] if ; inline
 
 [ 10 ] [
diff --git a/extra/benchmark/backtrack/backtrack.factor b/extra/benchmark/backtrack/backtrack.factor
new file mode 100644
index 0000000000..e9a5ad0ed8
--- /dev/null
+++ b/extra/benchmark/backtrack/backtrack.factor
@@ -0,0 +1,65 @@
+! Copyright (C) 2008 Slava Pestov.
+! See http://factorcode.org/license.txt for BSD license.
+USING: backtrack shuffle math math.ranges quotations locals fry
+kernel words io memoize macros io prettyprint sequences assocs
+combinators namespaces ;
+IN: benchmark.backtrack
+
+! This was suggested by Dr_Ford. Compute the number of quadruples
+! (a,b,c,d) with 1 <= a,b,c,d <= 10 such that we can make 24 by
+! placing them on the stack, and applying the operations
+! +, -, * and rot as many times as we wish.
+
+: nop ;
+
+MACRO: amb-execute ( seq -- quot )
+    [ length ] [ <enum> [ 1quotation ] assoc-map ] bi
+    '[ , amb , case ] ;
+
+: if-amb ( true false -- )
+    [
+        [ { t f } amb ]
+        [ '[ @ require t ] ]
+        [ '[ @ f ] ]
+        tri* if
+    ] with-scope ; inline
+
+: do-something ( a b -- c )
+    { + - * } amb-execute ;
+
+: some-rots ( a b c -- a b c )
+    #! Try to rot 0, 1 or 2 times.
+    { nop rot -rot } amb-execute ;
+
+MEMO: 24-from-1 ( a -- ? )
+    24 = ;
+
+MEMO: 24-from-2 ( a b -- ? )
+    [ do-something 24-from-1 ] [ 2drop ] if-amb ;
+
+MEMO: 24-from-3 ( a b c -- ? )
+    [ some-rots do-something 24-from-2 ] [ 3drop ] if-amb ;
+
+MEMO: 24-from-4 ( a b c d -- ? )
+    [ some-rots do-something 24-from-3 ] [ 4drop ] if-amb ;
+
+: find-impossible-24 ( -- n )
+    1 10 [a,b] [| a |
+        1 10 [a,b] [| b |
+            1 10 [a,b] [| c |
+                1 10 [a,b] [| d |
+                    a b c d 24-from-4
+                ] count
+            ] sigma
+        ] sigma
+    ] sigma ;
+
+: words { 24-from-1 24-from-2 24-from-3 24-from-4 } ;
+
+: backtrack-benchmark ( -- )
+    words [ reset-memoized ] each
+    find-impossible-24 pprint "/10000 quadruples can make 24." print
+    words [
+        dup pprint " tested " write "memoize" word-prop assoc-size pprint
+        " possibilities" print
+    ] each ;
diff --git a/extra/channels/channels-tests.factor b/extra/channels/channels-tests.factor
index df72572c67..3300faa125 100755
--- a/extra/channels/channels-tests.factor
+++ b/extra/channels/channels-tests.factor
@@ -17,7 +17,7 @@ IN: channels.tests
     from 
 ] unit-test
 
-{ V{ 1 2 3 4 } } [
+{ { 1 2 3 4 } } [
     V{ } clone <channel>
     [ from swap push ] in-thread
     [ from swap push ] in-thread
@@ -30,7 +30,7 @@ IN: channels.tests
     natural-sort
 ] unit-test
 
-{ V{ 1 2 4 9 } } [
+{ { 1 2 4 9 } } [
     V{ } clone <channel>
     [ 4 swap to ] in-thread
     [ 2 swap to ] in-thread
diff --git a/extra/multi-methods/tests/canonicalize.factor b/extra/multi-methods/tests/canonicalize.factor
index d5baf4914c..991551c009 100644
--- a/extra/multi-methods/tests/canonicalize.factor
+++ b/extra/multi-methods/tests/canonicalize.factor
@@ -49,7 +49,7 @@ kernel strings ;
         { { object ppc object } "b" }
         { { string object windows } "c" }
     }
-    V{ cpu os }
+    { cpu os }
 ] [
     example-1 canonicalize-specializers
 ] unit-test