diff --git a/basis/debugger/debugger.factor b/basis/debugger/debugger.factor
index bb0268f048..7994c3ed96 100644
--- a/basis/debugger/debugger.factor
+++ b/basis/debugger/debugger.factor
@@ -251,8 +251,15 @@ M: already-disposed summary drop "Attempting to operate on disposed object" ;
 M: no-current-vocab summary
     drop "Not in a vocabulary; IN: form required" ;
 
-M: no-word-error error.
-    "No word named ``" write name>> write "'' found in current vocabulary search path" print ;
+M: no-word-error summary
+    name>> "No word named ``" "'' found in current vocabulary search path" surround ;
+
+M: no-word-error error. summary print ;
+
+M: ambiguous-use-error summary
+    words>> first name>> "More than one vocabulary defines a word named ``" "''" surround ;
+
+M: ambiguous-use-error error. summary print ;
 
 M: staging-violation summary
     drop
diff --git a/basis/ui/tools/listener/listener.factor b/basis/ui/tools/listener/listener.factor
index 2e89482c3d..e12e59d259 100644
--- a/basis/ui/tools/listener/listener.factor
+++ b/basis/ui/tools/listener/listener.factor
@@ -55,7 +55,9 @@ M: vocab-completion (word-at-caret)
     drop dup vocab-exists? [ >vocab-link ] [ drop f ] if ;
 
 M: word-completion (word-at-caret)
-    manifest>> dup [ search-manifest ] [ 2drop f ] if ;
+    manifest>> dup [
+        '[ _ _ search-manifest ] [ drop f ] recover
+    ] [ 2drop f ] if ;
 
 M: char-completion (word-at-caret)
     2drop f ;
diff --git a/core/parser/parser-tests.factor b/core/parser/parser-tests.factor
index 16f08d474a..5cbcc14184 100644
--- a/core/parser/parser-tests.factor
+++ b/core/parser/parser-tests.factor
@@ -608,4 +608,16 @@ EXCLUDE: qualified.tests.bar => x ;
 
 [ t ] [
     "z" "parser.tests.forward-ref-3" lookup def>> [ vocabulary>> ] map all-equal?
-] unit-test
\ No newline at end of file
+] unit-test
+
+[ [ dup ] ] [
+    "USE: kernel dup" <string-reader> "unuse-test" parse-stream
+] unit-test
+
+[
+    "dup" <string-reader> "unuse-test" parse-stream
+] [ error>> error>> error>> no-word-error? ] must-fail-with
+
+[
+    "USE: kernel UNUSE: kernel dup" <string-reader> "unuse-test" parse-stream
+] [ error>> error>> error>> no-word-error? ] must-fail-with
\ No newline at end of file
diff --git a/core/vocabs/parser/parser.factor b/core/vocabs/parser/parser.factor
index 43451b4c86..ba4fb265c3 100644
--- a/core/vocabs/parser/parser.factor
+++ b/core/vocabs/parser/parser.factor
@@ -8,8 +8,21 @@ IN: vocabs.parser
 
 ERROR: no-word-error name ;
 
+: word-restarts ( possibilities -- restarts )
+    natural-sort
+    [ [ vocabulary>> "Use the " " vocabulary" surround ] keep ] { } map>assoc ;
+
+: word-restarts-with-defer ( name possibilities -- restarts )
+    word-restarts
+    swap "Defer word in current vocabulary" swap 2array
+    suffix ;
+
+: <no-word-error> ( name possibilities -- error restarts )
+    [ drop \ no-word-error boa ] [ word-restarts-with-defer ] 2bi ;
+
 TUPLE: manifest
 current-vocab
+{ search-vocab-names hashtable }
 { search-vocabs vector }
 { qualified-vocabs vector }
 { extra-words vector }
@@ -17,6 +30,7 @@ current-vocab
 
 : <manifest> ( -- manifest )
     manifest new
+        H{ } clone >>search-vocab-names
         V{ } clone >>search-vocabs
         V{ } clone >>qualified-vocabs
         V{ } clone >>extra-words
@@ -24,6 +38,7 @@ current-vocab
 
 M: manifest clone
     call-next-method
+        [ clone ] change-search-vocab-names
         [ clone ] change-search-vocabs
         [ clone ] change-qualified-vocabs
         [ clone ] change-extra-words
@@ -40,12 +55,10 @@ C: <extra-words> extra-words
 
 : clear-manifest ( -- )
     manifest get
+    [ search-vocab-names>> clear-assoc ]
     [ search-vocabs>> delete-all ]
     [ qualified-vocabs>> delete-all ]
-    bi ;
-
-: (use-vocab) ( vocab -- vocab seq )
-    load-vocab manifest get search-vocabs>> ;
+    tri ;
 
 : (add-qualified) ( qualified -- )
     manifest get qualified-vocabs>> push ;
@@ -87,19 +100,33 @@ TUPLE: no-current-vocab ;
     manifest get current-vocab>> vocab-name ".private" ?tail
     [ set-current-vocab ] [ drop ] if ;
 
-: use-vocab ( vocab -- ) (use-vocab) push ;
+: using-vocab? ( vocab -- ? )
+    vocab-name manifest get search-vocab-names>> key? ;
+
+: use-vocab ( vocab -- )
+    dup using-vocab?
+    [ drop ] [
+        manifest get
+        [ [ vocab-name ] dip search-vocab-names>> conjoin ]
+        [ [ load-vocab ] dip search-vocabs>> push ]
+        2bi
+    ] if ;
 
 : auto-use-vocab ( vocab -- )
     [ use-vocab ] [ manifest get auto-used>> push ] bi ;
 
 : auto-used? ( -- ? ) manifest get auto-used>> length 0 > ;
 
-: unuse-vocab ( vocab -- ) (use-vocab) delq ;
+: unuse-vocab ( vocab -- )
+    dup using-vocab? [
+        manifest get
+        [ [ vocab-name ] dip search-vocab-names>> delete-at ]
+        [ [ load-vocab ] dip search-vocabs>> delq ]
+        2bi
+    ] [ drop ] if ;
 
 : only-use-vocabs ( vocabs -- )
-    clear-manifest
-    [ vocab ] V{ } map-as sift
-    manifest get search-vocabs>> push-all ;
+    clear-manifest [ vocab ] filter [ use-vocab ] each ;
 
 TUPLE: qualified vocab prefix words ;
 
@@ -141,7 +168,10 @@ TUPLE: rename word vocab words ;
 
 : unuse-words ( assoc -- ) (use-words) delete ;
 
-ERROR: ambiguous-use-error words ;
+TUPLE: ambiguous-use-error words ;
+
+: <ambiguous-use-error> ( words -- error restarts )
+    [ \ ambiguous-use-error boa ] [ word-restarts ] bi ;
 
 <PRIVATE
 
@@ -154,7 +184,10 @@ ERROR: ambiguous-use-error words ;
     (vocab-search) {
         { 0 [ drop f ] }
         { 1 [ first ] }
-        [ drop ambiguous-use-error ]
+        [
+            drop <ambiguous-use-error> throw-restarts
+            dup [ vocabulary>> ] [ name>> 1array ] bi add-words-from
+        ]
     } case ;
 
 : qualified-search ( name manifest -- word/f )
@@ -168,12 +201,3 @@ PRIVATE>
 
 : search ( name -- word/f )
     manifest get search-manifest ;
-
-: word-restarts ( name possibilities -- restarts )
-    natural-sort
-    [ [ vocabulary>> "Use the " " vocabulary" surround ] keep ] { } map>assoc
-    swap "Defer word in current vocabulary" swap 2array
-    suffix ;
-
-: <no-word-error> ( name possibilities -- error restarts )
-    [ drop \ no-word-error boa ] [ word-restarts ] 2bi ;