diff --git a/core/vocabs/vocabs-tests.factor b/core/vocabs/vocabs-tests.factor
index 21c3668148..ec486e3a5a 100644
--- a/core/vocabs/vocabs-tests.factor
+++ b/core/vocabs/vocabs-tests.factor
@@ -3,3 +3,11 @@ USING: vocabs tools.test ;
 IN: vocabs.tests
 
 [ f ] [ "kernel" vocab-main ] unit-test
+
+[ t ] [ "" "" child-vocab? ] unit-test
+[ t ] [ "" "io.files" child-vocab? ] unit-test
+[ t ] [ "io" "io.files" child-vocab? ] unit-test
+[ f ] [ "io.files" "io" child-vocab? ] unit-test
+
+[ t ] [ "io.files" "io" parent-vocab? ] unit-test
+[ f ] [ "io" "io.files" parent-vocab? ] unit-test
diff --git a/core/vocabs/vocabs.factor b/core/vocabs/vocabs.factor
index 38881673e9..f023472c68 100644
--- a/core/vocabs/vocabs.factor
+++ b/core/vocabs/vocabs.factor
@@ -111,6 +111,12 @@ ERROR: no-vocab name ;
 : child-vocabs ( vocab -- seq )
     vocab-name vocabs [ child-vocab? ] with filter ;
 
+: parent-vocab? ( suffix name -- ? )
+    swap child-vocab? ;
+
+: parent-vocabs ( vocab -- seq )
+    vocab-name vocabs [ parent-vocab? ] with filter ;
+
 GENERIC: >vocab-link ( name -- vocab )
 
 M: vocab-spec >vocab-link ;