1 files changed, 1 insertions, 0 deletions

diff --git a/docker/Dockerfile b/docker/Dockerfile

index 4523c60645..ccc6a9f778 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,3 +1,4 @@
+# syntax=docker/dockerfile:1
 # Dockerfile to build the matrixdotorg/synapse docker images.
 #
 # Note that it uses features which are only available in BuildKit - see