diff --git a/build/Dockerfile b/build/Dockerfile
index 5cd6161..e07e60d 100644
--- a/build/Dockerfile
+++ b/build/Dockerfile
@@ -1,3 +1,8 @@
+#
+# The CI only rebuilds this Dockerfile if its hash changes.
+# Do not reference any external files, since modifications to them won't trigger a rebuild.
+#
+
 FROM fedora:30
 
 RUN dnf -y upgrade && \