diff --git a/core/threads/threads-docs.factor b/core/threads/threads-docs.factor
index fa79906cdf..d157907cc2 100755
--- a/core/threads/threads-docs.factor
+++ b/core/threads/threads-docs.factor
@@ -19,8 +19,7 @@ ARTICLE: "threads-yield" "Yielding and suspending threads"
 { $subsection yield }
 "Sleeping for a period of time:"
 { $subsection sleep }
-"Interruptible sleep:"
-{ $subsection nap }
+"Interrupting sleep:"
 { $subsection interrupt }
 "Threads can be suspended and woken up at some point in the future when a condition is satisfied:"
 { $subsection suspend }
@@ -106,14 +105,17 @@ HELP: stop
 HELP: yield
 { $description "Adds the current thread to the end of the run queue, and switches to the next runnable thread." } ;
 
+HELP: sleep-until
+{ $values { "time/f" "a non-negative integer or " { $link f } } }
+{ $description "Suspends the current thread until the given time, or indefinitely if a value of " { $link f } " is passed in."
+$nl
+"Other threads may interrupt the sleep by calling " { $link interrupt } "." } ;
+
 HELP: sleep
 { $values { "ms" "a non-negative integer" } }
-{ $description "Suspends the current thread for " { $snippet "ms" } " milliseconds." }
-{ $errors "Throws an error if another thread interrupted the sleep with " { $link interrupt } "." } ;
-
-HELP: nap
-{ $values { "ms/f" "a non-negative integer or " { $link f } } { "?" "a boolean indicating whether the thread was interrupted" } }
-{ $description "Suspends the current thread until another thread interrupts it with " { $link interrupt } ". If the input parameter is not " { $link f } ", then the thread will also wake up if the timeout expires before an interrupt is received." } ;
+{ $description "Suspends the current thread for " { $snippet "ms" } " milliseconds."
+$nl
+"Other threads may interrupt the sleep by calling " { $link interrupt } "." } ;
 
 HELP: interrupt
 { $values { "thread" thread } }
diff --git a/core/threads/threads.factor b/core/threads/threads.factor
index 70ed44e539..490c8dc740 100755
--- a/core/threads/threads.factor
+++ b/core/threads/threads.factor
@@ -75,12 +75,15 @@ PRIVATE>
 : sleep-queue 43 getenv ;
 
 : resume ( thread -- )
+    f over set-thread-state
     check-registered run-queue push-front ;
 
 : resume-now ( thread -- )
+    f over set-thread-state
     check-registered run-queue push-back ;
 
 : resume-with ( obj thread -- )
+    f over set-thread-state
     check-registered 2array run-queue push-front ;
 
 <PRIVATE
@@ -131,34 +134,27 @@ PRIVATE>
         self swap call next
     ] callcc1 2nip ; inline
 
-: yield ( -- ) [ resume ] "yield" suspend drop ;
+: yield ( -- ) [ resume ] f suspend drop ;
 
-GENERIC: nap-until ( time -- ? )
+GENERIC: sleep-until ( time/f -- )
 
-M: integer nap-until [ schedule-sleep ] curry "sleep" suspend ;
+M: integer sleep-until
+    [ schedule-sleep ] curry "sleep" suspend drop ;
 
-M: f nap-until drop [ drop ] "interrupt" suspend ;
+M: f sleep-until
+    drop [ drop ] "interrupt" suspend drop ;
 
-GENERIC: nap ( time -- ? )
+GENERIC: sleep ( ms -- )
 
-M: real nap millis + >integer nap-until ;
-
-M: f nap nap-until ;
-
-: sleep-until ( time -- )
-    nap-until [ "Sleep interrupted" throw ] when ;
-
-: sleep ( time -- )
-    nap [ "Sleep interrupted" throw ] when ;
+M: real sleep
+    millis + >integer sleep-until ;
 
 : interrupt ( thread -- )
-    dup self eq? [
-        drop
-    ] [
+    dup thread-state [
         dup thread-sleep-entry [ sleep-queue heap-delete ] when*
         f over set-thread-sleep-entry
-        t swap resume-with
-    ] if ;
+        dup resume
+    ] when drop ;
 
 : (spawn) ( thread -- )
     [
@@ -204,6 +200,7 @@ M: f nap nap-until ;
     initial-thread global
     [ drop f "Initial" [ die ] <thread> ] cache
     <box> over set-thread-continuation
+    f over set-thread-state
     dup register-thread
     set-self ;
 
diff --git a/extra/alarms/alarms.factor b/extra/alarms/alarms.factor
index 92a7c488ef..7f43dbd612 100755
--- a/extra/alarms/alarms.factor
+++ b/extra/alarms/alarms.factor
@@ -62,7 +62,7 @@ SYMBOL: alarm-thread
 
 : alarm-thread-loop ( -- )
     alarms get-global
-    dup next-alarm nap-until drop
+    dup next-alarm sleep-until
     dup trigger-alarms
     alarm-thread-loop ;
 
diff --git a/extra/calendar/calendar.factor b/extra/calendar/calendar.factor
index d1d7246a58..d834698d08 100755
--- a/extra/calendar/calendar.factor
+++ b/extra/calendar/calendar.factor
@@ -473,9 +473,9 @@ M: timestamp year. ( timestamp -- )
 : seconds-since-midnight ( timestamp -- x )
     dup beginning-of-day timestamp- ;
 
-M: timestamp nap-until timestamp>millis nap-until ;
+M: timestamp sleep-until timestamp>millis sleep-until ;
 
-M: dt nap from-now nap-until ;
+M: dt sleep from-now sleep-until ;
 
 {
     { [ unix? ] [ "calendar.unix" ] }
diff --git a/extra/io/windows/launcher/launcher.factor b/extra/io/windows/launcher/launcher.factor
index 58e3c0ba69..708dc1dc38 100755
--- a/extra/io/windows/launcher/launcher.factor
+++ b/extra/io/windows/launcher/launcher.factor
@@ -146,8 +146,8 @@ M: windows-io kill-process* ( handle -- )
 
 : wait-loop ( -- )
     processes get dup assoc-empty?
-    [ drop f nap drop ]
-    [ wait-for-processes [ 100 nap drop ] when ] if ;
+    [ drop f sleep-until ]
+    [ wait-for-processes [ 100 sleep ] when ] if ;
 
 SYMBOL: wait-thread
 
diff --git a/extra/tools/threads/threads.factor b/extra/tools/threads/threads.factor
index 3313a56964..552247e2c4 100755
--- a/extra/tools/threads/threads.factor
+++ b/extra/tools/threads/threads.factor
@@ -8,7 +8,10 @@ heaps.private system math math.parser ;
 : thread. ( thread -- )
     dup thread-id pprint-cell
     dup thread-name over [ write-object ] with-cell
-    dup thread-state "running" or [ write ] with-cell
+    dup thread-state [
+        [ dup self eq? "running" "yield" ? ] unless*
+        write
+    ] with-cell
     [
         thread-sleep-entry [
             entry-key millis [-] number>string write