diff --git a/communication_techniques/lancement.sh b/communication_techniques/lancement.sh
index 70e8f26..a17f094 100755
--- a/communication_techniques/lancement.sh
+++ b/communication_techniques/lancement.sh
@@ -1,5 +1,7 @@
 #! /bin/bash
 
+set -u
+
 # Files and directories
 binDir="bin"
 calcDir="calculation"
@@ -24,15 +26,13 @@ logFileName="\$perfDirName/cache_\$typeCache-nbProd_\$nbProd-typeProd_\$typeProd
 expDirName="logs"
 perfDirName="$expDirName/perfCommMulti-`date +'%F-%Hh%Mm%S'`"
 
-if [ -n "${LD_LIBRARY_PATH}" ]
+if [ -n "${LD_LIBRARY_PATH:-}" ] # If LD_LIBRARY_PATH is unbound then the expansion is "null" value
 then
 	LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${PHLDir}/${PHLLibDir}:${PAPIDir}/${PAPILibDir}:${PAPIDir}/${PAPILibDir}/${PAPIPFMDir}"
 else
 	LD_LIBRARY_PATH="${PHLDir}/${PHLLibDir}:${PAPIDir}/${PAPILibDir}:${PAPIDir}/${PAPILibDir}/${PAPIPFMDir}"
 fi
 
-set -u
-
 PAPILibPresent=""
 PFMLibPresent=""
 papiHighLevelLibPresent=""