diff --git a/tests/runtest b/tests/runtest
index 041be918..dc4699ee 100755
--- a/tests/runtest
+++ b/tests/runtest
@@ -23,14 +23,14 @@ BASEPATH=`pwd`
 cd dstress
 
 # remove excessive tests
-sed -e 's/torture-//g' -i '' Makefile
+sed -i -e 's/torture-//g' Makefile
 
 # make sure only .d files in 'run' tests are run
-sed -e 's/find run -type f |/find run -type f -name "*\\\\.d" |/' -i '' Makefile
-sed -e 's/find norun -type f |/find norun -type f -name "*\\\\.d" |/' -i '' Makefile
+sed -i -e 's/find run -type f |/find run -type f -name "*\\\\.d" |/' Makefile
+sed -i -e 's/find norun -type f |/find norun -type f -name "*\\\\.d" |/' Makefile
 
 # impose more conservative constraints (10s and 256 MB)
-sed -e 's/crashRun 30 1000/crashRun 10 256/' -i '' dstress.c
+sed -i -e 's/crashRun 30 1000/crashRun 10 256/' dstress.c
 
 echo
 echo "Running new test and storing result in $TARGETFILE ..."