diff --git a/core/classes/classes-tests.factor b/core/classes/classes-tests.factor
index 7eaa6c0e12..1dee6a095c 100755
--- a/core/classes/classes-tests.factor
+++ b/core/classes/classes-tests.factor
@@ -6,154 +6,6 @@ classes.algebra vectors definitions source-files
 compiler.units kernel.private sorting vocabs ;
 IN: classes.tests
 
-! DEFER: bah
-! FORGET: bah
-UNION: bah fixnum alien ;
-[ bah ] [ \ bah? "predicating" word-prop ] unit-test
-
-! Test redefinition of classes
-UNION: union-1 fixnum float ;
-
-GENERIC: generic-update-test ( x -- y )
-
-M: union-1 generic-update-test drop "union-1" ;
-
-[ f ] [ bignum union-1 class<= ] unit-test
-[ t ] [ union-1 number class<= ] unit-test
-[ "union-1" ] [ 1.0 generic-update-test ] unit-test
-
-"IN: classes.tests USE: math USE: arrays UNION: union-1 rational array ;" eval
-
-[ t ] [ bignum union-1 class<= ] unit-test
-[ f ] [ union-1 number class<= ] unit-test
-[ "union-1" ] [ { 1.0 } generic-update-test ] unit-test
-
-"IN: classes.tests USE: math PREDICATE: union-1 < integer even? ;" eval
-
-[ f ] [ union-1 union-class? ] unit-test
-[ t ] [ union-1 predicate-class? ] unit-test
-[ "union-1" ] [ 8 generic-update-test ] unit-test
-[ -7 generic-update-test ] must-fail
-
-! Test mixins
-MIXIN: sequence-mixin
-
-INSTANCE: array sequence-mixin
-INSTANCE: vector sequence-mixin
-INSTANCE: slice sequence-mixin
-
-MIXIN: assoc-mixin
-
-INSTANCE: hashtable assoc-mixin
-
-GENERIC: collection-size ( x -- y )
-
-M: sequence-mixin collection-size length ;
-
-M: assoc-mixin collection-size assoc-size ;
-
-[ t ] [ array sequence-mixin class<= ] unit-test
-[ t ] [ { 1 2 3 } sequence-mixin? ] unit-test
-[ 3 ] [ { 1 2 3 } collection-size ] unit-test
-[ f ] [ H{ { 1 2 } { 2 3 } } sequence-mixin? ] unit-test
-[ t ] [ H{ { 1 2 } { 2 3 } } assoc-mixin? ] unit-test
-[ 2 ] [ H{ { 1 2 } { 2 3 } } collection-size ] unit-test
-
-! Test mixing in of new classes after the fact
-DEFER: mx1
-FORGET: mx1
-
-MIXIN: mx1
-
-INSTANCE: integer mx1
-
-[ t ] [ integer mx1 class<= ] unit-test
-[ t ] [ mx1 integer class<= ] unit-test
-[ t ] [ mx1 number class<= ] unit-test
-
-"IN: classes.tests USE: arrays INSTANCE: array mx1" eval
-
-[ t ] [ array mx1 class<= ] unit-test
-[ f ] [ mx1 number class<= ] unit-test
-
-[ \ mx1 forget ] with-compilation-unit
-
-! Empty unions were causing problems
-GENERIC: empty-union-test ( obj -- obj )
-
-UNION: empty-union-1 ;
-
-M: empty-union-1 empty-union-test ;
-
-UNION: empty-union-2 ;
-
-M: empty-union-2 empty-union-test ;
-
-! Redefining a class didn't update containing unions
-UNION: redefine-bug-1 fixnum ;
-
-UNION: redefine-bug-2 redefine-bug-1 quotation ;
-
-[ t ] [ fixnum redefine-bug-2 class<= ] unit-test
-[ t ] [ quotation redefine-bug-2 class<= ] unit-test
-
-[ ] [ "IN: classes.tests USE: math UNION: redefine-bug-1 bignum ;" eval ] unit-test
-
-[ t ] [ bignum redefine-bug-1 class<= ] unit-test
-[ f ] [ fixnum redefine-bug-2 class<= ] unit-test
-[ t ] [ bignum redefine-bug-2 class<= ] unit-test
-
-USE: io.streams.string
-
-2 [
-    [ "mixin-forget-test" forget-source ] with-compilation-unit
-    
-    [ ] [
-        {
-            "USING: sequences ;"
-            "IN: classes.tests"
-            "MIXIN: mixin-forget-test"
-            "INSTANCE: sequence mixin-forget-test"
-            "GENERIC: mixin-forget-test-g ( x -- y )"
-            "M: mixin-forget-test mixin-forget-test-g ;"
-        } "\n" join <string-reader> "mixin-forget-test"
-        parse-stream drop
-    ] unit-test
-    
-    [ { } ] [ { } "mixin-forget-test-g" "classes.tests" lookup execute ] unit-test
-    [ H{ } "mixin-forget-test-g" "classes.tests" lookup execute ] must-fail
-    
-    [ ] [
-        {
-            "USING: hashtables ;"
-            "IN: classes.tests"
-            "MIXIN: mixin-forget-test"
-            "INSTANCE: hashtable mixin-forget-test"
-            "GENERIC: mixin-forget-test-g ( x -- y )"
-            "M: mixin-forget-test mixin-forget-test-g ;"
-        } "\n" join <string-reader> "mixin-forget-test"
-        parse-stream drop
-    ] unit-test
-    
-    [ { } "mixin-forget-test-g" "classes.tests" lookup execute ] must-fail
-    [ H{ } ] [ H{ } "mixin-forget-test-g" "classes.tests" lookup execute ] unit-test
-] times
-
-! Method flattening interfered with mixin update
-MIXIN: flat-mx-1
-TUPLE: flat-mx-1-1 ; INSTANCE: flat-mx-1-1 flat-mx-1
-TUPLE: flat-mx-1-2 ; INSTANCE: flat-mx-1-2 flat-mx-1
-TUPLE: flat-mx-1-3 ; INSTANCE: flat-mx-1-3 flat-mx-1
-TUPLE: flat-mx-1-4 ; INSTANCE: flat-mx-1-4 flat-mx-1
-MIXIN: flat-mx-2     INSTANCE: flat-mx-2 flat-mx-1
-TUPLE: flat-mx-2-1 ; INSTANCE: flat-mx-2-1 flat-mx-2
-
-[ t ] [ T{ flat-mx-2-1 } flat-mx-1? ] unit-test
-
-! Test generic see and parsing
-[ "USING: alien math ;\nIN: classes.tests\nUNION: bah fixnum alien ;\n" ]
-[ [ \ bah see ] with-string-writer ] unit-test
-
 [ t ] [ 3 object instance? ] unit-test
 [ t ] [ 3 fixnum instance? ] unit-test
 [ f ] [ 3 float instance? ] unit-test
diff --git a/core/classes/classes.factor b/core/classes/classes.factor
index 0e10b85735..56c3b0a0ab 100755
--- a/core/classes/classes.factor
+++ b/core/classes/classes.factor
@@ -72,6 +72,7 @@ M: class reset-class
         "superclass"
         "members"
         "participants"
+        "predicate"
     } reset-props ;
 
 M: word reset-class drop ;
@@ -87,8 +88,9 @@ GENERIC: implementors ( class/classes -- seq )
         tri
     ] { } make ;
 
-: class-usages ( class -- seq )
-    [ update-map get at ] closure keys ;
+: class-usage ( class -- seq ) update-map get at ;
+
+: class-usages ( class -- seq ) [ class-usage ] closure keys ;
 
 <PRIVATE
 
@@ -163,16 +165,20 @@ GENERIC: update-methods ( class seq -- )
 : forget-methods ( class -- )
     [ implementors ] [ [ swap 2array ] curry ] bi map forget-all ;
 
+GENERIC: class-forgotten ( use class -- )
+
 : forget-class ( class -- )
-    class-usages [
-        {
-            [ forget-predicate ]
-            [ forget-methods ]
-            [ implementors-map- ]
-            [ update-map- ]
-            [ reset-class ]
-        } cleave
-    ] each ;
+    {
+        [ dup class-usage keys [ class-forgotten ] with each ]
+        [ forget-predicate ]
+        [ forget-methods ]
+        [ implementors-map- ]
+        [ update-map- ]
+        [ reset-class ]
+    } cleave ;
+
+M: class class-forgotten
+    nip forget-class ;
 
 M: class forget* ( class -- )
     [ call-next-method ] [ forget-class ] bi ;
diff --git a/core/classes/mixin/mixin-tests.factor b/core/classes/mixin/mixin-tests.factor
new file mode 100644
index 0000000000..b455676c38
--- /dev/null
+++ b/core/classes/mixin/mixin-tests.factor
@@ -0,0 +1,107 @@
+USING: alien arrays definitions generic assocs hashtables io
+kernel math namespaces parser prettyprint sequences strings
+tools.test vectors words quotations classes
+classes.private classes.union classes.mixin classes.predicate
+classes.algebra vectors definitions source-files
+compiler.units kernel.private sorting vocabs ;
+IN: classes.mixin.tests
+
+! Test mixins
+MIXIN: sequence-mixin
+
+INSTANCE: array sequence-mixin
+INSTANCE: vector sequence-mixin
+INSTANCE: slice sequence-mixin
+
+MIXIN: assoc-mixin
+
+INSTANCE: hashtable assoc-mixin
+
+GENERIC: collection-size ( x -- y )
+
+M: sequence-mixin collection-size length ;
+
+M: assoc-mixin collection-size assoc-size ;
+
+[ t ] [ array sequence-mixin class<= ] unit-test
+[ t ] [ { 1 2 3 } sequence-mixin? ] unit-test
+[ 3 ] [ { 1 2 3 } collection-size ] unit-test
+[ f ] [ H{ { 1 2 } { 2 3 } } sequence-mixin? ] unit-test
+[ t ] [ H{ { 1 2 } { 2 3 } } assoc-mixin? ] unit-test
+[ 2 ] [ H{ { 1 2 } { 2 3 } } collection-size ] unit-test
+
+! Test mixing in of new classes after the fact
+DEFER: mx1
+FORGET: mx1
+
+MIXIN: mx1
+
+INSTANCE: integer mx1
+
+[ t ] [ integer mx1 class<= ] unit-test
+[ t ] [ mx1 integer class<= ] unit-test
+[ t ] [ mx1 number class<= ] unit-test
+
+"IN: classes.mixin.tests USE: arrays INSTANCE: array mx1" eval
+
+[ t ] [ array mx1 class<= ] unit-test
+[ f ] [ mx1 number class<= ] unit-test
+
+[ \ mx1 forget ] with-compilation-unit
+
+USE: io.streams.string
+
+2 [
+    [ "mixin-forget-test" forget-source ] with-compilation-unit
+    
+    [ ] [
+        {
+            "USING: sequences ;"
+            "IN: classes.mixin.tests"
+            "MIXIN: mixin-forget-test"
+            "INSTANCE: sequence mixin-forget-test"
+            "GENERIC: mixin-forget-test-g ( x -- y )"
+            "M: mixin-forget-test mixin-forget-test-g ;"
+        } "\n" join <string-reader> "mixin-forget-test"
+        parse-stream drop
+    ] unit-test
+    
+    [ { } ] [ { } "mixin-forget-test-g" "classes.mixin.tests" lookup execute ] unit-test
+    [ H{ } "mixin-forget-test-g" "classes.mixin.tests" lookup execute ] must-fail
+    
+    [ ] [
+        {
+            "USING: hashtables ;"
+            "IN: classes.mixin.tests"
+            "MIXIN: mixin-forget-test"
+            "INSTANCE: hashtable mixin-forget-test"
+            "GENERIC: mixin-forget-test-g ( x -- y )"
+            "M: mixin-forget-test mixin-forget-test-g ;"
+        } "\n" join <string-reader> "mixin-forget-test"
+        parse-stream drop
+    ] unit-test
+    
+    [ { } "mixin-forget-test-g" "classes.mixin.tests" lookup execute ] must-fail
+    [ H{ } ] [ H{ } "mixin-forget-test-g" "classes.mixin.tests" lookup execute ] unit-test
+] times
+
+! Method flattening interfered with mixin update
+MIXIN: flat-mx-1
+TUPLE: flat-mx-1-1 ; INSTANCE: flat-mx-1-1 flat-mx-1
+TUPLE: flat-mx-1-2 ; INSTANCE: flat-mx-1-2 flat-mx-1
+TUPLE: flat-mx-1-3 ; INSTANCE: flat-mx-1-3 flat-mx-1
+TUPLE: flat-mx-1-4 ; INSTANCE: flat-mx-1-4 flat-mx-1
+MIXIN: flat-mx-2     INSTANCE: flat-mx-2 flat-mx-1
+TUPLE: flat-mx-2-1 ; INSTANCE: flat-mx-2-1 flat-mx-2
+
+[ t ] [ T{ flat-mx-2-1 } flat-mx-1? ] unit-test
+
+! Too eager with reset-class
+
+[ ] [ "IN: classes.mixin.tests MIXIN: blah SINGLETON: boo INSTANCE: boo blah" <string-reader> "mixin-reset-test" parse-stream drop ] unit-test
+
+[ t ] [ "blah" "classes.mixin.tests" lookup mixin-class? ] unit-test
+
+[ ] [ "IN: classes.mixin.tests MIXIN: blah" <string-reader> "mixin-reset-test" parse-stream drop ] unit-test
+
+[ t ] [ "blah" "classes.mixin.tests" lookup mixin-class? ] unit-test
diff --git a/core/classes/mixin/mixin.factor b/core/classes/mixin/mixin.factor
index 050c99a430..a08d4ed20c 100755
--- a/core/classes/mixin/mixin.factor
+++ b/core/classes/mixin/mixin.factor
@@ -65,6 +65,8 @@ TUPLE: check-mixin-class mixin ;
         update-classes
     ] [ 2drop ] if-mixin-member? ;
 
+M: mixin-class class-forgotten remove-mixin-instance ;
+
 ! Definition protocol implementation ensures that removing an
 ! INSTANCE: declaration from a source file updates the mixin.
 TUPLE: mixin-instance loc class mixin ;
diff --git a/core/classes/tuple/tuple.factor b/core/classes/tuple/tuple.factor
index 830ace3bf6..83d85b68d8 100755
--- a/core/classes/tuple/tuple.factor
+++ b/core/classes/tuple/tuple.factor
@@ -260,8 +260,13 @@ M: tuple-class define-tuple-class
 
 : define-error-class ( class superclass slots -- )
     [ define-tuple-class ]
-    [ [ dup [ boa throw ] curry ] [ drop ] [ thrower-effect ] tri* ] 3bi
-    define-declared ;
+    [ 2drop reset-generic ]
+    [
+        [ dup [ boa throw ] curry ]
+        [ drop ]
+        [ thrower-effect ]
+        tri* define-declared
+    ] 3tri ;
 
 M: tuple-class reset-class
     [
diff --git a/core/classes/union/union-tests.factor b/core/classes/union/union-tests.factor
new file mode 100644
index 0000000000..6c7f25d577
--- /dev/null
+++ b/core/classes/union/union-tests.factor
@@ -0,0 +1,88 @@
+USING: alien arrays definitions generic assocs hashtables io
+kernel math namespaces parser prettyprint sequences strings
+tools.test vectors words quotations classes
+classes.private classes.union classes.mixin classes.predicate
+classes.algebra vectors definitions source-files
+compiler.units kernel.private sorting vocabs io.streams.string ;
+IN: classes.union.tests
+
+! DEFER: bah
+! FORGET: bah
+UNION: bah fixnum alien ;
+[ bah ] [ \ bah? "predicating" word-prop ] unit-test
+
+[ "USING: alien math ;\nIN: classes.tests\nUNION: bah fixnum alien ;\n" ]
+[ [ \ bah see ] with-string-writer ] unit-test
+
+! Test redefinition of classes
+UNION: union-1 fixnum float ;
+
+GENERIC: generic-update-test ( x -- y )
+
+M: union-1 generic-update-test drop "union-1" ;
+
+[ f ] [ bignum union-1 class<= ] unit-test
+[ t ] [ union-1 number class<= ] unit-test
+[ "union-1" ] [ 1.0 generic-update-test ] unit-test
+
+"IN: classes.union.tests USE: math USE: arrays UNION: union-1 rational array ;" eval
+
+[ t ] [ bignum union-1 class<= ] unit-test
+[ f ] [ union-1 number class<= ] unit-test
+[ "union-1" ] [ { 1.0 } generic-update-test ] unit-test
+
+"IN: classes.union.tests USE: math PREDICATE: union-1 < integer even? ;" eval
+
+[ f ] [ union-1 union-class? ] unit-test
+[ t ] [ union-1 predicate-class? ] unit-test
+[ "union-1" ] [ 8 generic-update-test ] unit-test
+[ -7 generic-update-test ] must-fail
+
+! Empty unions were causing problems
+GENERIC: empty-union-test ( obj -- obj )
+
+UNION: empty-union-1 ;
+
+M: empty-union-1 empty-union-test ;
+
+UNION: empty-union-2 ;
+
+M: empty-union-2 empty-union-test ;
+
+! Redefining a class didn't update containing unions
+UNION: redefine-bug-1 fixnum ;
+
+UNION: redefine-bug-2 redefine-bug-1 quotation ;
+
+[ t ] [ fixnum redefine-bug-2 class<= ] unit-test
+[ t ] [ quotation redefine-bug-2 class<= ] unit-test
+
+[ ] [ "IN: classes.union.tests USE: math UNION: redefine-bug-1 bignum ;" eval ] unit-test
+
+[ t ] [ bignum redefine-bug-1 class<= ] unit-test
+[ f ] [ fixnum redefine-bug-2 class<= ] unit-test
+[ t ] [ bignum redefine-bug-2 class<= ] unit-test
+
+! Too eager with reset-class
+
+[ ] [ "IN: classes.union.tests SINGLETON: foo UNION: blah foo ;" <string-reader> "union-reset-test" parse-stream drop ] unit-test
+
+[ t ] [ "blah" "classes.union.tests" lookup union-class? ] unit-test
+
+[ ] [ "IN: classes.union.tests USE: math UNION: blah integer ;" <string-reader> "union-reset-test" parse-stream drop ] unit-test
+
+[ t ] [ "blah" "classes.union.tests" lookup union-class? ] unit-test
+
+GENERIC: test-generic ( x -- y )
+
+TUPLE: a-tuple ;
+
+UNION: a-union a-tuple ;
+
+M: a-union test-generic ;
+
+[ f ] [ \ test-generic "methods" word-prop assoc-empty? ] unit-test
+
+[ ] [ [ \ a-tuple forget-class ] with-compilation-unit ] unit-test
+
+[ t ] [ \ test-generic "methods" word-prop assoc-empty? ] unit-test
diff --git a/core/syntax/syntax.factor b/core/syntax/syntax.factor
index ad3bfed77b..e8ee857877 100755
--- a/core/syntax/syntax.factor
+++ b/core/syntax/syntax.factor
@@ -175,7 +175,6 @@ IN: bootstrap.syntax
 
     "ERROR:" [
         parse-tuple-definition
-        pick reset-generic
         pick save-location
         define-error-class
     ] define-syntax