diff --git a/tools/dev/bash_profile b/tools/dev/bash_profile
index 3034375..aef0e5f 100644
--- a/tools/dev/bash_profile
+++ b/tools/dev/bash_profile
@@ -109,7 +109,7 @@
 # Applies the settings in the specified cell file or lists current cell definition
 # if no cell file is given.
 function cell {
-    cell=$1
+    cell=${1:-""}
     case "$cell" in
     "borrow")
         aux="/tmp/cell-$$"