diff --git a/basis/compiler/tests/optimizer.factor b/basis/compiler/tests/optimizer.factor
index 18679ce77b..0c9b1817c8 100644
--- a/basis/compiler/tests/optimizer.factor
+++ b/basis/compiler/tests/optimizer.factor
@@ -413,5 +413,35 @@ M: object bad-dispatch-position-test* ;
     ] with-compilation-unit
 ] unit-test
 
+[ 16 ] [
+    [
+        0 2
+        [
+            nip
+            [
+                1 + {
+                    [ 16 ]
+                    [ 16 ]
+                    [ 16 ]
+                } dispatch
+            ] [
+                {
+                    [ ]
+                    [ ]
+                    [ ]
+                } dispatch
+            ] bi
+        ] each-integer
+    ] compile-call
+] unit-test
+
+: dispatch-branch-problem ( a b c -- d )
+    dup 0 < [ "boo" throw ] when
+    1 + { [ + ] [ - ] [ * ] } dispatch ;
+
+[ 3 4 -1 dispatch-branch-problem ] [ "boo" = ] must-fail-with
+[ -1 ] [ 3 4 0 dispatch-branch-problem ] unit-test
+[ 12 ] [ 3 4 1 dispatch-branch-problem ] unit-test
+
 ! Not sure if I want to fix this...
 ! [ t [ [ f ] [ 3 ] if >fixnum ] compile-call ] [ no-method? ] must-fail-with
\ No newline at end of file
diff --git a/basis/compiler/tree/propagation/branches/branches.factor b/basis/compiler/tree/propagation/branches/branches.factor
index b8861a6292..0d837d82ae 100755
--- a/basis/compiler/tree/propagation/branches/branches.factor
+++ b/basis/compiler/tree/propagation/branches/branches.factor
@@ -1,8 +1,8 @@
-! Copyright (C) 2008 Slava Pestov.
+! Copyright (C) 2008, 2009 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: fry kernel sequences assocs accessors namespaces
 math.intervals arrays classes.algebra combinators columns
-stack-checker.branches locals
+stack-checker.branches locals math
 compiler.utilities
 compiler.tree
 compiler.tree.combinators
@@ -21,6 +21,9 @@ M: #if child-constraints
 M: #dispatch child-constraints
     children>> length f <repetition> ;
 
+! There is an important invariant here, either no flags are set
+! in live-branches, exactly one is set, or all are set.
+
 GENERIC: live-branches ( #branch -- indices )
 
 M: #if live-branches
@@ -32,8 +35,12 @@ M: #if live-branches
     } cond nip ;
 
 M: #dispatch live-branches
-    [ children>> length ] [ in-d>> first value-info interval>> ] bi
-    '[ _ interval-contains? ] map ;
+    [ children>> ] [ in-d>> first value-info ] bi {
+        { [ dup class>> null-class? ] [ drop length f <array> ] }
+        { [ dup literal>> integer? not ] [ drop length t <array> ] }
+        { [ 2dup literal>> swap bounds-check? not ] [ drop length t <array> ] }
+        [ literal>> swap length f <array> [ [ t ] 2dip set-nth ] keep ]
+    } cond ;
 
 : live-children ( #branch -- children )
     [ children>> ] [ live-branches>> ] bi select-children ;
diff --git a/basis/help/markup/markup-tests.factor b/basis/help/markup/markup-tests.factor
index 2e986c60d2..c7a1da02df 100644
--- a/basis/help/markup/markup-tests.factor
+++ b/basis/help/markup/markup-tests.factor
@@ -1,11 +1,14 @@
-USING: definitions help help.markup kernel sequences tools.test
-words parser namespaces assocs generic io.streams.string accessors
-strings math ;
+USING: accessors assocs definitions fry generic help
+help.markup io.streams.string kernel math namespaces parser
+sequences strings tools.test words ;
 IN: help.markup.tests
 
+: with-markup-test ( quot -- )
+    '[ f last-element set _ with-string-writer ] with-scope ; inline
+
 TUPLE: blahblah quux ;
 
-[ "int" ] [ [ { "int" } $instance ] with-string-writer ] unit-test
+[ "int" ] [ [ { "int" } $instance ] with-markup-test ] unit-test
 
 [ ] [ \ quux>> print-topic ] unit-test
 [ ] [ \ >>quux print-topic ] unit-test
@@ -18,54 +21,54 @@ TUPLE: blahblah quux ;
 [ ] [ gensym print-topic ] unit-test
 
 [ "a string" ]
-[ [ { $or string } print-element ] with-string-writer ] unit-test
+[ [ { $or string } print-element ] with-markup-test ] unit-test
 
 [ "a string or an integer" ]
-[ [ { $or string integer } print-element ] with-string-writer ] unit-test
+[ [ { $or string integer } print-element ] with-markup-test ] unit-test
 
 [ "a string, a fixnum, or an integer" ]
-[ [ { $or string fixnum integer } print-element ] with-string-writer ] unit-test
+[ [ { $or string fixnum integer } print-element ] with-markup-test ] unit-test
 
 ! Layout
 
 [ "span" ]
-[ [ { "span" } print-content ] with-string-writer ] unit-test
+[ [ { "span" } print-content ] with-markup-test ] unit-test
 
 [ "span1span2" ]
-[ [ { "span1" "span2" } print-content ] with-string-writer ] unit-test
+[ [ { "span1" "span2" } print-content ] with-markup-test ] unit-test
 
 [ "span1\n\nspan2" ]
-[ [ { "span1" { $nl } "span2" } print-content ] with-string-writer ] unit-test
+[ [ { "span1" { $nl } "span2" } print-content ] with-markup-test ] unit-test
 
 [ "\nspan" ]
-[ [ { { $nl } "span" } print-content ] with-string-writer ] unit-test
+[ [ { { $nl } "span" } print-content ] with-markup-test ] unit-test
 
 [ "2 2 +\nspan" ]
-[ [ { { $code "2 2 +" } "span" } print-content ] with-string-writer ] unit-test
+[ [ { { $code "2 2 +" } "span" } print-content ] with-markup-test ] unit-test
 
 [ "2 2 +" ]
-[ [ { { $code "2 2 +" } } print-content ] with-string-writer ] unit-test
+[ [ { { $code "2 2 +" } } print-content ] with-markup-test ] unit-test
 
 [ "span\n2 2 +" ]
-[ [ { "span" { $code "2 2 +" } } print-content ] with-string-writer ] unit-test
+[ [ { "span" { $code "2 2 +" } } print-content ] with-markup-test ] unit-test
 
 [ "\n2 2 +" ]
-[ [ { { $nl } { $code "2 2 +" } } print-content ] with-string-writer ] unit-test
+[ [ { { $nl } { $code "2 2 +" } } print-content ] with-markup-test ] unit-test
 
 [ "span\n\n2 2 +" ]
-[ [ { "span" { $nl } { $code "2 2 +" } } print-content ] with-string-writer ] unit-test
+[ [ { "span" { $nl } { $code "2 2 +" } } print-content ] with-markup-test ] unit-test
 
 [ "Heading" ]
-[ [ { { $heading "Heading" } } print-content ] with-string-writer ] unit-test
+[ [ { { $heading "Heading" } } print-content ] with-markup-test ] unit-test
 
 [ "Heading1\n\nHeading2" ]
-[ [ { { $heading "Heading1" } { $heading "Heading2" } } print-content ] with-string-writer ] unit-test
+[ [ { { $heading "Heading1" } { $heading "Heading2" } } print-content ] with-markup-test ] unit-test
 
 [ "span\n\nHeading" ]
-[ [ { "span" { $heading "Heading" } } print-content ] with-string-writer ] unit-test
+[ [ { "span" { $heading "Heading" } } print-content ] with-markup-test ] unit-test
 
 [ "\nHeading" ]
-[ [ { { $nl } { $heading "Heading" } } print-content ] with-string-writer ] unit-test
+[ [ { { $nl } { $heading "Heading" } } print-content ] with-markup-test ] unit-test
 
 [ "span\n\nHeading" ]
-[ [ { "span" { $nl } { $heading "Heading" } } print-content ] with-string-writer ] unit-test
+[ [ { "span" { $nl } { $heading "Heading" } } print-content ] with-markup-test ] unit-test