diff --git a/etc/rally.bash_completion b/etc/rally.bash_completion
index 8bb8ef0f..565c8040 100644
--- a/etc/rally.bash_completion
+++ b/etc/rally.bash_completion
@@ -50,8 +50,9 @@ _rally()
 
 
     for OPT in ${!OPTS[*]} ; do
-        CMDSUB=(${OPT//_/ })
-        SUBCOMMANDS[${CMDSUB[0]}]+="${CMDSUB[1]} "
+        CMD=${OPT%%_*}
+        CMDSUB=${OPT#*_}
+        SUBCOMMANDS[${CMD}]+="${CMDSUB} "
     done
 
     COMMANDS="${!SUBCOMMANDS[*]}"