Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 tests/docker/dockerfiles/debian9.docker | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/docker/dockerfiles/debian9.docker b/tests/docker/dockerfiles/debian9.docker
index 056e5389cc..a4509950e6 100644
--- a/tests/docker/dockerfiles/debian9.docker
+++ b/tests/docker/dockerfiles/debian9.docker
@@ -20,6 +20,7 @@ RUN DEBIAN_FRONTEND=noninteractive eatmydata \
         bison \
         build-essential \
         ca-certificates \
+        clang \
         flex \
         git \
         pkg-config \
-- 
2.13.2