diff --git a/async.zsh b/async.zsh
index 2b6ed01..7f61ce2 100644
--- a/async.zsh
+++ b/async.zsh
@@ -117,6 +117,10 @@ _async_worker() {
 	# pids of child processes.
 	unsetopt monitor
 
+	# Worker name, for debugging purposes.
+	local worker_name=$1
+	shift
+
 	# Redirect stderr to `/dev/null` in case unforseen errors produced by the
 	# worker. For example: `fork failed: resource temporarily unavailable`.
 	# Some older versions of zsh might also print malloc errors (know to happen
@@ -124,6 +128,7 @@ _async_worker() {
 	if ((ASYNC_DEBUG)); then
 		exec 2>>${ASYNC_DEBUG_WORKER_STDERR}
 		if [[ $ASYNC_DEBUG_WORKER_STDERR != /dev/null ]]; then
+			PROMPT4="(async):${worker_name}> ${PROMPT4}"
 			setopt xtrace
 		fi
 	else
@@ -635,9 +640,9 @@ async_start_worker() {
 	}
 
 	if (( errfd != -1 )); then
-		zpty -b $worker _async_worker -p $$ $args 2>&$errfd
+		zpty -b $worker _async_worker $worker -p $$ $args 2>&$errfd
 	else
-		zpty -b $worker _async_worker -p $$ $args
+		zpty -b $worker _async_worker $worker -p $$ $args
 	fi
 	local ret=$?
 
diff --git a/async_test.zsh b/async_test.zsh
index 6b58919..8b813fa 100644
--- a/async_test.zsh
+++ b/async_test.zsh
@@ -651,6 +651,14 @@ test_zle_watcher() {
 test_main() {
 	# Load zsh-async before running each test.
 	zmodload zsh/datetime
+	if [[ -o xtrace ]]; then
+		typeset -g ASYNC_DEBUG ASYNC_DEBUG_WORKER_STDERR
+		export ASYNC_DEBUG=1
+		# Output to special fd from test runner.
+		# TODO(mafredri):
+		exec 9> >(cat)
+		export ASYNC_DEBUG_WORKER_STDERR=/dev/fd/9
+	fi
 	. ./async.zsh
 	async_init
 }
diff --git a/test.zsh b/test.zsh
index 01ded81..a26c588 100755
--- a/test.zsh
+++ b/test.zsh
@@ -15,13 +15,13 @@ zmodload zsh/zselect
 TEST_GLOB=.
 TEST_RUN=
 TEST_VERBOSE=0
-TEST_TRACE=1
+TEST_TRACE=0
 TEST_CODE_SKIP=100
 TEST_CODE_ERROR=101
 TEST_CODE_TIMEOUT=102
 
 show_help() {
-	print "usage: ./test.zsh [-v] [-x] [-run pattern] [search pattern]"
+	print "usage: ./test.zsh [-h] [-v] [-x] [-d] [-run pattern] [search pattern]"
 }
 
 parse_opts() {