diff --git a/tests/Terminal_-_Detect_width.sh b/tests/Terminal_-_Detect_width.sh
index 63389cb..11958a5 100644
--- a/tests/Terminal_-_Detect_width.sh
+++ b/tests/Terminal_-_Detect_width.sh
@@ -17,25 +17,38 @@ if echo "kill-server" | tmux -C -L pvtest 2>&1 | grep -Fq "tmux: unknown option"
 	exit 2
 fi
 
-# Run a progress meter inside a terminal of the given width, and output the
-# longest number of characters seen between "[" and "]".
+# Run the given command $3 inside a terminal of the given width $1, waiting
+# $2 seconds, and output the results.
 #
-runWidthTest () {
+runInTerminal () {
 	terminalWidth="$1"
+	secondsToWait="$2"
+	commandToRun="$3"
 
 	{
 	echo "set remain-on-exit on"
-	echo "new-session -d"
+	echo "new-session -d -x ${terminalWidth} -y 5"
+	# starting the session doesn't always correctly set the size
 	echo "resize-window -x ${terminalWidth} -y 5"
+	# tmux 1.8 doesn't have "resize-window"
+	echo "resize-pane -x ${terminalWidth} -y 5"
 	echo "pipe-pane 'cat > ${workFile1}'"
-	echo "respawn-pane -k sh -c \"${testSubject} -pSs 1K </dev/zero >/dev/null\""
-	sleep 1
+	echo "respawn-pane -k \"${commandToRun}\""
+	sleep "${secondsToWait}"
 	echo "kill-server"
 	sleep 1
 	} \
 	| tmux -C -L pvtest >/dev/null
 
-	tr '\r' '\n' < "${workFile1}" \
+	cat "${workFile1}"
+}
+
+# Run a progress meter inside a terminal of the given width, and output the
+# longest number of characters seen between "[" and "]".
+#
+runWidthTest () {
+	runInTerminal "$1" 1 "${testSubject} -pSs 1K </dev/zero >/dev/null" \
+	| tr '\r' '\n' \
 	| sed -n 's/^.*\[//;s/\].*$//p' \
 	| awk 'BEGIN {m=0} {n=length($0); m=(n>m?n:m)} END {print m}'
 }
@@ -52,11 +65,21 @@ widthTest () {
 		echo "no output from test at width=${terminalWidth}"
 		exit 1
 	elif ! test "${longestBar}" -eq $((terminalWidth-7)); then
-		echo "bar size incorrect (${longestBar}) at width=${terminalWidth})"
+		echo "bar size incorrect (${longestBar}) at width=${terminalWidth}"
 		exit 1
 	fi
 }
 
+
+# Check that tmux can actually resize the terminal.
+checkSize="100"
+detectedWidth=$(runInTerminal "${checkSize}" 1 "stty -a | tr \\\";\\\" \\\"\\\\n\\\" | grep col | sed -n 1p | tr -dc 0-9")
+if ! test "${detectedWidth}" = "${checkSize}"; then
+	echo "test requires a \`tmux' that can resize a detached window (requested width ${checkSize}, detected ${detectedWidth})"
+	exit 2
+fi
+
+# Test the progress bar width at various terminal sizes.
 widthTest 80
 widthTest 120
 widthTest 400