diff --git a/src/main/java/org/olat/modules/bigbluebutton/manager/BigBlueButtonUriBuilder.java b/src/main/java/org/olat/modules/bigbluebutton/manager/BigBlueButtonUriBuilder.java
index 7779d2c80564cd2286dbd18074a8896a905e7400..dd2d71132ce1b2b21b5f01ea743f90fb4333f7bc 100644
--- a/src/main/java/org/olat/modules/bigbluebutton/manager/BigBlueButtonUriBuilder.java
+++ b/src/main/java/org/olat/modules/bigbluebutton/manager/BigBlueButtonUriBuilder.java
@@ -150,7 +150,7 @@ public class BigBlueButtonUriBuilder {
     private static String checksum(String s) {
     	String checksum = "";
     	try {
-    		checksum = org.apache.commons.codec.digest.DigestUtils.sha256Hex(s);
+    		checksum = org.apache.commons.codec.digest.DigestUtils.sha1Hex(s);
     	} catch (Exception e) {
     		log.error("Cannot calculate checksum", e);
     	}