diff --git a/changelog.d/5490.bugfix b/changelog.d/5490.bugfix
new file mode 100644
index 0000000000000000000000000000000000000000..4242254c53b882b1be085501cf8b19e2278754b2
--- /dev/null
+++ b/changelog.d/5490.bugfix
@@ -0,0 +1 @@
+Fix failure to start under docker with SAML support enabled.
\ No newline at end of file
diff --git a/docker/Dockerfile b/docker/Dockerfile
index c35da67a2aade6574cd3765bae86f9f67f33c292..24921eb098c174e637c5a3dbbb51e49acf40132f 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -57,6 +57,7 @@ RUN pip install --prefix="/install" --no-warn-script-location \
 
 FROM docker.io/python:${PYTHON_VERSION}-alpine3.8
 
+# xmlsec is required for saml support
 RUN apk add --no-cache --virtual .runtime_deps \
         libffi \
         libjpeg-turbo \
@@ -64,7 +65,8 @@ RUN apk add --no-cache --virtual .runtime_deps \
         libxslt \
         libpq \
         zlib \
-        su-exec
+        su-exec \
+        xmlsec
 
 COPY --from=builder /install /usr/local
 COPY ./docker/start.py /start.py