diff --git a/basis/bootstrap/image/image.factor b/basis/bootstrap/image/image.factor
index c99b047686..3552f0bd92 100644
--- a/basis/bootstrap/image/image.factor
+++ b/basis/bootstrap/image/image.factor
@@ -545,7 +545,7 @@ M: quotation '
     \ c-to-factor c-to-factor-word set
     \ lazy-jit-compile lazy-jit-compile-word set
     \ unwind-native-frames unwind-native-frames-word set
-    [ undefined ] undefined-quot set ;
+    undefined-def undefined-quot set ;
 
 : emit-special-objects ( -- )
     special-objects get keys [ emit-special-object ] each ;
diff --git a/basis/debugger/debugger.factor b/basis/debugger/debugger.factor
index d5284133b2..ba90d761cc 100644
--- a/basis/debugger/debugger.factor
+++ b/basis/debugger/debugger.factor
@@ -236,7 +236,10 @@ M: redefine-error error.
     def>> . ;
 
 M: undefined summary
-    drop "Calling a deferred word before it has been defined" ;
+    word>> undefined?
+    "Cannot call a deferred word before it has been defined"
+    "Cannot call a word before it has been compiled"
+    ? ;
 
 M: no-compilation-unit error.
     "Attempting to define " write
diff --git a/basis/prettyprint/prettyprint.factor b/basis/prettyprint/prettyprint.factor
index 65d25f1812..ccc77068e6 100644
--- a/basis/prettyprint/prettyprint.factor
+++ b/basis/prettyprint/prettyprint.factor
@@ -1,10 +1,10 @@
-! Copyright (C) 2003, 2009 Slava Pestov.
+! Copyright (C) 2003, 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: arrays accessors assocs colors combinators grouping io
 io.streams.string io.styles kernel make math math.parser namespaces
 parser prettyprint.backend prettyprint.config prettyprint.custom
 prettyprint.sections quotations sequences sorting strings vocabs
-vocabs.prettyprint words sets ;
+vocabs.prettyprint words sets generic ;
 IN: prettyprint
 
 : with-use ( obj quot -- )
@@ -72,24 +72,31 @@ SYMBOL: ->
     ] [ ] make ;
 
 : remove-breakpoints ( quot pos -- quot' )
+    1 + short cut [ (remove-breakpoints) ] bi@ [ -> ] glue ;
+
+: callframe. ( triple -- )
+    first3
+    [
+        {
+            { [ dup method-body? ] [ "Method: " write . ] }
+            { [ dup word? ] [ "Word: " write . ] }
+            [ drop ]
+        } cond
+    ] 2dip
     over quotation? [
-        1 + short cut [ (remove-breakpoints) ] bi@
-        [ -> ] glue
-    ] [
-        drop
-    ] if ;
-
-PRIVATE>
-
-: callstack. ( callstack -- )
-    callstack>array 2 <groups> [
+        "Quotation: " write
         remove-breakpoints
         [
             3 nesting-limit set
             100 length-limit set
             .
         ] with-scope
-    ] assoc-each ;
+    ] [ 2drop ] if ;
+
+PRIVATE>
+
+: callstack. ( callstack -- )
+    callstack>array 3 <groups> [ nl ] [ callframe. ] interleave ;
 
 : .c ( -- ) callstack callstack. ;
 
diff --git a/core/syntax/syntax.factor b/core/syntax/syntax.factor
index dfb3e0bc10..cf2c49fff9 100644
--- a/core/syntax/syntax.factor
+++ b/core/syntax/syntax.factor
@@ -135,7 +135,7 @@ IN: bootstrap.syntax
 
     "DEFER:" [
         scan current-vocab create
-        [ fake-definition ] [ set-word ] [ [ undefined ] define ] tri
+        [ fake-definition ] [ set-word ] [ undefined-def define ] tri
     ] define-core-syntax
     
     "ALIAS:" [
diff --git a/core/words/words-tests.factor b/core/words/words-tests.factor
index 46b20bf2e6..2734defaac 100644
--- a/core/words/words-tests.factor
+++ b/core/words/words-tests.factor
@@ -64,9 +64,14 @@ FORGET: forgotten
 FORGET: another-forgotten
 : another-forgotten ( -- ) ;
 
+! Make sure that undefined words throw proper errors
+DEFER: deferred
+[ deferred ] [ T{ undefined f deferred } = ] must-fail-with
 
-DEFER: x
-[ x ] [ undefined? ] must-fail-with
+[ "IN: words.tests DEFER: not-compiled << not-compiled >>" eval( -- ) ]
+[ error>> [ undefined? ] [ word>> name>> "not-compiled" = ] bi and ] must-fail-with
+
+[ ] [ "IN: words.tests FORGET: not-compiled" eval( -- ) ] unit-test
 
 [ ] [ [ "no-loc" "words.tests" create drop ] with-compilation-unit ] unit-test
 [ f ] [ "no-loc" "words.tests" lookup where ] unit-test
diff --git a/core/words/words.factor b/core/words/words.factor
index 4fe00d1edf..6c6e0d188b 100644
--- a/core/words/words.factor
+++ b/core/words/words.factor
@@ -32,9 +32,22 @@ M: word definition def>> ;
 
 : reset-props ( word seq -- ) [ remove-word-prop ] with each ;
 
-ERROR: undefined ;
+<PRIVATE
 
-PREDICATE: deferred < word ( obj -- ? ) def>> [ undefined ] = ;
+: caller ( callstack -- word ) callstack>array <reversed> third ;
+
+PRIVATE>
+
+TUPLE: undefined word ;
+: undefined ( -- * ) callstack caller \ undefined boa throw ;
+
+: undefined-def ( -- quot )
+    #! 'f' inhibits tail call optimization in non-optimizing
+    #! compiler, ensuring that we can pull out the caller word
+    #! above.
+    [ undefined f ] ;
+
+PREDICATE: deferred < word ( obj -- ? ) def>> undefined-def = ;
 M: deferred definer drop \ DEFER: f ;
 M: deferred definition drop f ;
 
diff --git a/vm/callstack.cpp b/vm/callstack.cpp
index 4aa9321353..195b212d8b 100755
--- a/vm/callstack.cpp
+++ b/vm/callstack.cpp
@@ -132,10 +132,12 @@ struct stack_frame_accumulator {
 
 	void operator()(stack_frame *frame)
 	{
-		data_root<object> executing(parent->frame_executing_quot(frame),parent);
+		data_root<object> executing_quot(parent->frame_executing_quot(frame),parent);
+		data_root<object> executing(parent->frame_executing(frame),parent);
 		data_root<object> scan(parent->frame_scan(frame),parent);
 
 		frames.add(executing.value());
+		frames.add(executing_quot.value());
 		frames.add(scan.value());
 	}
 };