diff --git a/tools/run_tests/post_tests_c.sh b/tools/run_tests/post_tests_c.sh
index f2f3ce9432d..4409526dab2 100755
--- a/tools/run_tests/post_tests_c.sh
+++ b/tools/run_tests/post_tests_c.sh
@@ -34,8 +34,12 @@ if [ "$CONFIG" != "gcov" ] ; then exit ; fi
 
 root=$(readlink -f $(dirname $0)/../..)
 out=$root/reports/c_cxx_coverage
-tmp=$(mktemp)
+tmp1=$(mktemp)
+tmp2=$(mktemp)
 cd $root
-lcov --capture --directory . --output-file $tmp
-genhtml $tmp --output-directory $out
-rm $tmp
+lcov --capture --directory . --output-file $tmp1
+lcov --extract $tmp1 "$root/src/*" "$root/include/*" --output-file $tmp2
+genhtml $tmp2 --output-directory $out
+rm $tmp2
+rm $tmp1
+