diff --git a/MCwrapper/MakeMC.csh b/MCwrapper/MakeMC.csh
index 4b5ee933..3d3f3d9d 100755
--- a/MCwrapper/MakeMC.csh
+++ b/MCwrapper/MakeMC.csh
@@ -235,8 +235,8 @@ if ("$GENR" != "0") then
 	else if ("$GEANTVER" == "4") then
 	#make run.mac then call it below
 	rm -f run.mac
-	echo /run/beamOn $EVT_TO_GEN >> run.mac
-	echo "exit" >> run.mac
+	echo "/run/beamOn $EVT_TO_GEN" > run.mac
+	echo "exit" >>! run.mac
 	hdgeant4 -t$NUMTHREADS run.mac
 	rm run.mac
 	else
diff --git a/MCwrapper/MakeMC.sh b/MCwrapper/MakeMC.sh
index 71618de9..36951846 100755
--- a/MCwrapper/MakeMC.sh
+++ b/MCwrapper/MakeMC.sh
@@ -235,8 +235,8 @@ if [[ "$GENR" != "0" ]]; then
 	elif [[ "$GEANTVER" -eq "4" ]]; then
 	    #make run.mac then call it below
 	    rm -f run.mac
-	    echo /run/beamOn $EVT_TO_GEN >> run.mac
-	    echo "exit" >> run.mac
+	    echo "/run/beamOn $EVT_TO_GEN" >run.mac
+	    echo "exit" >>! run.mac
 	    hdgeant4 -t$NUMTHREADS run.mac
 	    rm run.mac
 	else