diff --git a/test/libexec/tmuxifier-tmux-test.sh b/test/libexec/tmuxifier-tmux-test.sh
index b634184..fa54e00 100755
--- a/test/libexec/tmuxifier-tmux-test.sh
+++ b/test/libexec/tmuxifier-tmux-test.sh
@@ -8,8 +8,6 @@ source "${root}/lib/util.sh"
 
 # Setup.
 libexec="${root}/libexec"
-realTMUX="$TMUX"
-unset TMUX
 export TMUXIFIER_TMUX_OPTS="-L tmuxifier-tests"
 tmux $TMUXIFIER_TMUX_OPTS new -d -s foobar
 tmux $TMUXIFIER_TMUX_OPTS new -d -s dude
@@ -21,8 +19,6 @@ assert "${libexec}/tmuxifier-tmux list-sessions -F \"- #{session_name}\"" \
 # Tear down.
 tmux $TMUXIFIER_TMUX_OPTS kill-server
 unset TMUXIFIER_TMUX_OPTS
-TMUX="$realTMUX"
-unset realTMUX
 
 # End of tests.
 assert_end "tmuxifier-tmux"
diff --git a/test/test-helper.sh b/test/test-helper.sh
index 39d09e6..773c18a 100644
--- a/test/test-helper.sh
+++ b/test/test-helper.sh
@@ -27,6 +27,10 @@ root="$(abs_dirname "$testroot/../..")"
 # Set TMUXIFIER environment variable
 TMUXIFIER="$root"
 
+# Unset TMUX environment variable, tests assume they're not running within
+# Tmux.
+unset TMUX
+
 # Unset various Tmuxifier environment variables to prevent a local install of
 # Tmuxifier interfering with tests.
 unset TMUXIFIER_LAYOUT_PATH