diff --git a/src/runner.sh b/src/runner.sh
index fb35a30..47292d1 100755
--- a/src/runner.sh
+++ b/src/runner.sh
@@ -546,8 +546,9 @@ main() (
 			fail "Runner process with pid='${pid}' is not running." \
 				"${err_runner_process_not_running}"
 		fi
-		if ! kill "${pid}" || kill -KILL "${pid}"; then
-			fail "Cannot kill runner process." "${err_runner_process_not_killed}"
+		if ! output="$(kill "${pid}" || kill -KILL "${pid}")"; then
+			fail "Cannot kill runner process: ${output}." \
+				"${err_runner_process_not_killed}"
 		fi
 		rm --force "${runner_sock}"
 		;;