diff --git a/containers/jug/setup_detectors.py b/containers/jug/setup_detectors.py
index e515d08425a7a49e2c0534826b82a7ae746d6431..0ddfa02a3e499b82e725dc3bfb30cd632b67eda3 100755
--- a/containers/jug/setup_detectors.py
+++ b/containers/jug/setup_detectors.py
@@ -24,7 +24,7 @@ export JUGGLER_INSTALL_PREFIX=/usr/local
 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:{prefix}/lib
 
 ## modify PS1 for this detector version
-export PS1="${{PS1}}"
+export PS1="${{PS1:-}}"
 export PS1="{branch}${{PS1_SIGIL}}>${{PS1#*>}}"
 unset branch
 '''