diff --git a/scripts/partial_tempering.sh b/scripts/partial_tempering.sh
index 2e5f1832bac6276ef3c72e19c21ef3a0afd649ba..d4ba669853604c516ee19998dd0b6c94fbb0181d 100755
--- a/scripts/partial_tempering.sh
+++ b/scripts/partial_tempering.sh
@@ -58,7 +58,7 @@ fi
 
 gromacs5=1
 
-if [ $1 == --gromacs4 ] ; then
+if [ "$1" == --gromacs4 ] ; then
   gromacs5=0
   shift
 fi