diff --git a/extra/nested-comments/nested-comments-tests.factor b/extra/nested-comments/nested-comments-tests.factor
new file mode 100644
index 0000000000..2c446dc229
--- /dev/null
+++ b/extra/nested-comments/nested-comments-tests.factor
@@ -0,0 +1,43 @@
+! Copyright (C) 2009 Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: accessors eval kernel lexer nested-comments tools.test ;
+IN: nested-comments.tests
+
+! Correct
+[ ] [
+    "USE: nested-comments (* comment *)" eval( -- )
+] unit-test
+
+[ ] [
+    "USE: nested-comments (* comment*)" eval( -- )
+] unit-test
+
+[ ] [
+    "USE: nested-comments (* comment
+*)" eval( -- )
+] unit-test
+
+[ ] [
+    "USE: nested-comments (* comment
+*)" eval( -- )
+] unit-test
+
+[ ] [
+    "USE: nested-comments (* comment
+*)" eval( -- )
+] unit-test
+
+[ ] [
+    "USE: nested-comments (* comment
+    (* *)
+
+*)" eval( -- )
+] unit-test
+
+! Malformed
+[
+    "USE: nested-comments (* comment
+    (* *)" eval( -- )
+] [
+    error>> T{ unexpected f "*)" f } =
+] must-fail-with
diff --git a/extra/nested-comments/nested-comments.factor b/extra/nested-comments/nested-comments.factor
index 94daffec2d..9c85574c80 100644
--- a/extra/nested-comments/nested-comments.factor
+++ b/extra/nested-comments/nested-comments.factor
@@ -1,20 +1,22 @@
-! by blei on #concatenative
+! Copyright (C) 2009 blei, Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
 USING: kernel sequences math locals make multiline ;
 IN: nested-comments
 
-:: (subsequences-at) ( sseq seq n -- )
-    sseq seq n start*
-    [ dup , sseq length + [ sseq seq ] dip (subsequences-at) ]
-    when* ;
+: (count-subsequences) ( count substring string n -- count' )
+    [ 2dup ] dip start* [
+        pick length +
+        [ 1 + ] 3dip (count-subsequences)
+    ] [
+        2drop
+    ] if* ;
 
-: subsequences-at ( sseq seq -- indices )
-    [ 0 (subsequences-at) ] { } make ;
+: count-subsequences ( subseq seq -- n )
+    [ 0 ] 2dip 0 (count-subsequences) ;
 
-: count-subsequences ( sseq seq -- i )
-    subsequences-at length ;
+: parse-nestable-comment ( parsed-vector left-to-parse -- parsed-vector )
+    1 - "*)" parse-multiline-string
+    [ "(*" ] dip
+    count-subsequences + dup 0 > [ parse-nestable-comment ] [ drop ] if ;
 
-: parse-all-(* ( parsed-vector left-to-parse -- parsed-vector )
-    1 - "*)" parse-multiline-string [ "(*" ] dip
-    count-subsequences + dup 0 > [ parse-all-(* ] [ drop ] if ;
-
-SYNTAX: (* 1 parse-all-(* ;
\ No newline at end of file
+SYNTAX: (* 1 parse-nestable-comment ;