diff --git a/extra/modern/modern.factor b/extra/modern/modern.factor
index df06a86306..e042b0f2a9 100644
--- a/extra/modern/modern.factor
+++ b/extra/modern/modern.factor
@@ -7,7 +7,7 @@ sequences.generalizations sets shuffle splitting strings
 syntax.modern unicode vocabs.loader ;
 IN: modern
 
-ERROR: string-expected-got-eof string n ;
+ERROR: unexpected-eof string n ;
 ERROR: long-opening-mismatch tag open string n ch ;
 ERROR: lex-expected-but-got-eof string n expected ;
 ERROR: expected-length-tokens string n length seq ;
@@ -123,14 +123,14 @@ MACRO:: read-matched ( ch -- quot: ( string n tag -- string n' slice' ) )
             { char: \\ [ drop next-char-from drop read-string-payload ] }
         } case
     ] [
-        string-expected-got-eof
+        unexpected-eof
     ] if ;
 
 :: read-string ( string n tag -- string n' seq )
     string n read-string-payload nip :> n'
     string
     n'
-    n' [ string n string-expected-got-eof ] unless
+    n' [ string n unexpected-eof ] unless
     n n' 1 - string <slice>
     n' 1 - n' string <slice>
     tag -rot 3array ;
@@ -157,8 +157,11 @@ MACRO:: read-matched ( ch -- quot: ( string n tag -- string n' slice' ) )
 : read-lowercase-colon ( string n slice -- string n' lowercase-colon )
     dup [ char: \: = ] count-tail
     '[
-        _ [ slice-til-not-whitespace drop [ lex-factor ] dip swap 2array ] replicate
-        ensure-no-false dup [ token-expected ] unless
+        _ [
+            slice-til-not-whitespace drop ! XXX: whitespace here
+            [ dup [ unexpected-eof ] unless ] dip
+            [ lex-factor ] dip swap 2array
+        ] replicate
         dup terminator? [ unexpected-terminator ] when
     ] dip swap 2array ;
 
diff --git a/extra/modern/slices/slices-tests.factor b/extra/modern/slices/slices-tests.factor
new file mode 100644
index 0000000000..164151d871
--- /dev/null
+++ b/extra/modern/slices/slices-tests.factor
@@ -0,0 +1,46 @@
+! Copyright (C) 2019 Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: ascii modern.slices sequences tools.test ;
+IN: modern.slices.tests
+
+{ "foo:" f f f } [
+    "foo:" f slice-til-not-whitespace
+] unit-test
+
+{ "foo:" f f f } [
+    "foo:" f slice-til-whitespace
+] unit-test
+
+{ "foo:" 0 T{ slice f 0 0 "foo:" } 102 } [
+    "foo:" 0 slice-til-not-whitespace
+] unit-test
+
+{ "foo:" 3 T{ slice f 3 3 "foo:" } 58 } [
+    "foo:" 3 slice-til-not-whitespace
+] unit-test
+
+{ "foo:" f T{ slice f 0 4 "foo:" } f } [
+    "foo:" 0 slice-til-whitespace
+] unit-test
+
+{ "foo:" f T{ slice f 3 4 "foo:" } f } [
+    "foo:" 3 slice-til-whitespace
+] unit-test
+
+{
+    "foo "
+    f
+    T{ slice f 0 4 "foo " }
+    f
+} [
+    "foo " 0 [ blank? ] slice-until-include
+] unit-test
+
+{
+    "foo "
+    3
+    T{ slice f 0 3 "foo " }
+    32
+} [
+    "foo " 0 [ blank? ] slice-until-exclude
+] unit-test
\ No newline at end of file
diff --git a/extra/modern/slices/slices.factor b/extra/modern/slices/slices.factor
index c87916ba78..b966b88e7b 100644
--- a/extra/modern/slices/slices.factor
+++ b/extra/modern/slices/slices.factor
@@ -52,17 +52,25 @@ ERROR: unexpected-end string n ;
     swapd find-from* ; inline
 
 : slice-until-exclude ( string n quot -- string n' slice/f ch/f )
-    [ drop ]
-    [ find-from' ] 3bi ! ( string n n' ch )
-    [ drop nip ]
-    [ [ rot ?<slice> ] dip ] 4bi ; inline
+    over [
+        [ drop ]
+        [ find-from' ] 3bi ! ( string n n' ch )
+        [ drop nip ]
+        [ [ rot ?<slice> ] dip ] 4bi
+    ] [
+        drop f f
+    ] if ; inline
 
 : slice-until-include ( string n tokens -- string n' slice/f ch/f )
-    '[ _ member? ]
-    [ drop ]
-    [ find-from' [ ?1+ ] dip ] 3bi ! ( string n n' ch )
-    [ drop nip ]
-    [ [ rot ?<slice> ] dip ] 4bi ; inline
+    over [
+        '[ _ member? ]
+        [ drop ]
+        [ find-from' [ ?1+ ] dip ] 3bi ! ( string n n' ch )
+        [ drop nip ]
+        [ [ rot ?<slice> ] dip ] 4bi
+    ] [
+        drop f f
+    ] if ; inline
 
 : slice-til-whitespace ( string n -- string n' slice/f ch/f )
     [ "\s\r\n" member? ] slice-until-exclude ; inline