diff --git a/build.sh b/build.sh
index 083559aa..c237fe83 100755
--- a/build.sh
+++ b/build.sh
@@ -21,7 +21,7 @@ SMB=${SMB:-no}
 # Install directory prefix
 PREFIX=/tmp/local
 # For TESTrun
-export TCPDUMP_BIN=/tmp/local/bin/tcpdump
+export TCPDUMP_BIN=$PREFIX/bin/tcpdump
 
 travis_fold() {
     local action="$1"
diff --git a/build_matrix.sh b/build_matrix.sh
index 1e610a9b..fc3b7707 100755
--- a/build_matrix.sh
+++ b/build_matrix.sh
@@ -70,7 +70,7 @@ build_tcpdump() {
 choose_libpcap() {
     if [ "$BUILD_LIBPCAP" = no ]; then
         echo_magenta 'Use system libpcap'
-        rm -rf /tmp/local
+        rm -rf $PREFIX
     else
         # Build libpcap with autoconf
         CMAKE_SAVE=$CMAKE