diff --git a/CMakeLists.txt b/CMakeLists.txt
index 34c123775..a509614cf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -104,7 +104,7 @@ if(ENABLE_TESTING)
     )
 
   ADD_CUSTOM_TARGET(memcheck
-    COMMAND sed -i .bak s+/usr/bin/valgrind+`which valgrind`+ DartConfiguration.tcl
+    COMMAND sed -i.bak s+/usr/bin/valgrind+`which valgrind`+ DartConfiguration.tcl
     COMMAND ctest -O memcheck.log -D ExperimentalMemCheck
     COMMAND tail -n1 memcheck.log | grep 'Memory checking results:' > /dev/null
     COMMAND rm -f memcheck.log