diff --git a/core/classes/mixin/mixin-tests.factor b/core/classes/mixin/mixin-tests.factor
index cd11591d6c..f44642fdd5 100644
--- a/core/classes/mixin/mixin-tests.factor
+++ b/core/classes/mixin/mixin-tests.factor
@@ -119,3 +119,13 @@ MIXIN: move-instance-declaration-mixin
 [ ] [ "IN: classes.mixin.tests.a" <string-reader> "move-mixin-test-1" parse-stream drop ] unit-test
 
 [ { string } ] [ move-instance-declaration-mixin members ] unit-test
+
+MIXIN: silly-mixin
+SYMBOL: not-a-class
+
+[ [ \ not-a-class \ silly-mixin add-mixin-instance ] with-compilation-unit ] must-fail
+
+SYMBOL: not-a-mixin
+TUPLE: a-class ;
+
+[ [ \ a-class \ not-a-mixin add-mixin-instance ] with-compilation-unit ] must-fail
diff --git a/core/classes/mixin/mixin.factor b/core/classes/mixin/mixin.factor
index 4bdb893d9a..6cf95716be 100644
--- a/core/classes/mixin/mixin.factor
+++ b/core/classes/mixin/mixin.factor
@@ -50,7 +50,9 @@ TUPLE: check-mixin-class class ;
     [ [ f ] 2dip "instances" word-prop set-at ]
     2bi ;
 
-: add-mixin-instance ( class mixin -- )
+GENERIC# add-mixin-instance 1 ( class mixin -- )
+
+M: class add-mixin-instance
     #! Note: we call update-classes on the new member, not the
     #! mixin. This ensures that we only have to update the
     #! methods whose specializer intersects the new member, not
diff --git a/core/generic/generic.factor b/core/generic/generic.factor
index 965be91642..4b398f6532 100644
--- a/core/generic/generic.factor
+++ b/core/generic/generic.factor
@@ -164,8 +164,8 @@ M: sequence update-methods ( class seq -- )
         drop
         2dup [ "combination" word-prop ] dip = [ 2drop ] [
             {
+                [ drop reset-generic ]
                 [ "combination" set-word-prop ]
-                [ drop "methods" word-prop values forget-all ]
                 [ drop H{ } clone "methods" set-word-prop ]
                 [ define-default-method ]
             }
diff --git a/core/generic/single/single-tests.factor b/core/generic/single/single-tests.factor
index 8245cbe22f..c8cab970fd 100644
--- a/core/generic/single/single-tests.factor
+++ b/core/generic/single/single-tests.factor
@@ -4,7 +4,7 @@ generic.single strings sequences arrays kernel accessors words
 specialized-arrays.double byte-arrays bit-arrays parser namespaces
 make quotations stack-checker vectors growable hashtables sbufs
 prettyprint byte-vectors bit-vectors specialized-vectors.double
-definitions generic sets graphs assocs grouping see ;
+definitions generic sets graphs assocs grouping see eval ;
 
 GENERIC: lo-tag-test ( obj -- obj' )
 
@@ -269,3 +269,9 @@ M: growable call-next-hooker call-next-method "growable " prepend ;
 [ t ] [
     \ + \ nth effective-method nip dup \ nth "default-method" word-prop eq? and
 ] unit-test
+
+[ ] [ "IN: generic.single.tests GENERIC: xyz ( a -- b )" eval( -- ) ] unit-test
+[ ] [ "IN: generic.single.tests MATH: xyz ( a b -- c )" eval( -- ) ] unit-test
+
+[ f ] [ "xyz" "generic.single.tests" lookup direct-entry-def>> ] unit-test
+[ f ] [ "xyz" "generic.single.tests" lookup "decision-tree" word-prop ] unit-test
\ No newline at end of file
diff --git a/core/generic/standard/standard.factor b/core/generic/standard/standard.factor
index bf8ea8da08..6e2c80a2ce 100644
--- a/core/generic/standard/standard.factor
+++ b/core/generic/standard/standard.factor
@@ -1,12 +1,14 @@
 ! Copyright (C) 2009 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors definitions generic generic.single kernel
-namespaces words math combinators sequences ;
+namespaces words math math.order combinators sequences ;
 IN: generic.standard
 
 TUPLE: standard-combination < single-combination # ;
 
-C: <standard-combination> standard-combination
+: <standard-combination> ( n -- standard-combination )
+    dup 0 2 between? [ "Bad dispatch position" throw ] unless
+    standard-combination boa ;
 
 PREDICATE: standard-generic < generic
     "combination" word-prop standard-combination? ;
@@ -24,7 +26,6 @@ CONSTANT: simple-combination T{ standard-combination f 0 }
         { 0 [ [ dup ] ] }
         { 1 [ [ over ] ] }
         { 2 [ [ pick ] ] }
-        [ 1- (picker) [ dip swap ] curry ]
     } case ;
 
 M: standard-combination picker