diff --git a/guacamole-docker/bin/start.sh b/guacamole-docker/bin/start.sh
index 95c08cd40..bbdee9e2e 100755
--- a/guacamole-docker/bin/start.sh
+++ b/guacamole-docker/bin/start.sh
@@ -752,22 +752,33 @@ END
 associate_saml() {
 
     # Verify required parameters are present
-    if [ -z "$SAML_IDP_METADATA_URL" ]
+    if [ -z "$SAML_IDP_METADATA_URL" ] && \
+       [ -z "$SAML_ENTITY_ID" -o -z "$SAML_CALLBACK_URL" ]
     then
         cat <<END
 FATAL: Missing required environment variables
 -------------------------------------------------------------------------------
-If using a SAML authentication, you must provide each of the following
-environment variables:
+If using a SAML authentication, you must provide either SAML_IDP_METADATA_URL
+or both SAML_ENTITY_ID and SAML_CALLBACK_URL environment variables:
 
-    SAML_IDP_METADATA_URL           The URI of the XML metadata file that from the SAML Identity
-                                    Provider
+    SAML_IDP_METADATA_URL   The URI of the XML metadata file that from the SAML Identity
+                            Provider that contains all of the information the SAML
+                            extension needs in order to know how to authenticate with
+                            the IdP. This URI can either be a remote server (e.g. https://)
+                            or a local file on the filesystem (e.g. file://).
+
+    SAML_ENTITY_ID          The entity ID of the Guacamole SAML client, which is
+                            generally the URL of the Guacamole server
+
+    SAML_CALLBACK_URL       The URL that the IdP will use once authentication has
+                            succeeded to return to the Guacamole web application and
+                            provide the authentication details to the SAML extension.
 END
         exit 1;
     fi
 
     # Update config file
-    set_property          "saml-idp-metadata-url"            "$SAML_IDP_METADATA_URL"
+    set_optional_property "saml-idp-metadata-url"            "$SAML_IDP_METADATA_URL"
     set_optional_property "saml-idp-url"                     "$SAML_IDP_URL"
     set_optional_property "saml-entity-id"                   "$SAML_ENTITY_ID"
     set_optional_property "saml-callback-url"                "$SAML_CALLBACK_URL"