diff --git a/etc/taskcluster/docker/build.dockerfile b/etc/taskcluster/docker/build.dockerfile
index dea5112e2682..809eb74048f7 100644
--- a/etc/taskcluster/docker/build.dockerfile
+++ b/etc/taskcluster/docker/build.dockerfile
@@ -38,6 +38,9 @@ RUN \
         # sampling profiler
         libunwind-dev \
         #
+        # harfbuzz
+        ragel \
+        #
         #
     && \
     #