diff --git a/tests/common.sh b/tests/common.sh
index a3cc30f36..61757dbe7 100755
--- a/tests/common.sh
+++ b/tests/common.sh
@@ -40,12 +40,12 @@ function build_sketches()
     local build_arg=$3
     local build_dir=build.tmp
     mkdir -p $build_dir
-    rm -rf $build_dir/*
     local build_cmd="python tools/build.py -b generic -v -k -p $PWD/$build_dir $build_arg "
     local sketches=$(find $srcpath -name *.ino)
     print_size_info >size.log
     export ARDUINO_IDE_PATH=$arduino
     for sketch in $sketches; do
+        rm -rf $build_dir/*
         local sketchdir=$(dirname $sketch)
         local sketchdirname=$(basename $sketchdir)
         local sketchname=$(basename $sketch)