diff --git a/multiuser/api/che-multiuser-api-authentication-commons/src/main/java/org/eclipse/che/multiuser/api/authentication/commons/filter/MultiUserEnvironmentInitializationFilter.java b/multiuser/api/che-multiuser-api-authentication-commons/src/main/java/org/eclipse/che/multiuser/api/authentication/commons/filter/MultiUserEnvironmentInitializationFilter.java
index 2f2dfcbc5a..9939dc8802 100644
--- a/multiuser/api/che-multiuser-api-authentication-commons/src/main/java/org/eclipse/che/multiuser/api/authentication/commons/filter/MultiUserEnvironmentInitializationFilter.java
+++ b/multiuser/api/che-multiuser-api-authentication-commons/src/main/java/org/eclipse/che/multiuser/api/authentication/commons/filter/MultiUserEnvironmentInitializationFilter.java
@@ -11,6 +11,7 @@
  */
 package org.eclipse.che.multiuser.api.authentication.commons.filter;
 
+import static java.lang.String.format;
 import static org.eclipse.che.multiuser.api.authentication.commons.Constants.CHE_SUBJECT_ATTRIBUTE;
 
 import java.io.IOException;
@@ -28,6 +29,8 @@ import org.eclipse.che.commons.subject.Subject;
 import org.eclipse.che.multiuser.api.authentication.commons.SessionStore;
 import org.eclipse.che.multiuser.api.authentication.commons.SubjectHttpRequestWrapper;
 import org.eclipse.che.multiuser.api.authentication.commons.token.RequestTokenExtractor;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Performs basic environment initialization actions as follows:
@@ -44,6 +47,9 @@ import org.eclipse.che.multiuser.api.authentication.commons.token.RequestTokenEx
  */
 public abstract class MultiUserEnvironmentInitializationFilter implements Filter {
 
+  private static final Logger LOG =
+      LoggerFactory.getLogger(MultiUserEnvironmentInitializationFilter.class);
+
   private final SessionStore sessionStore;
   private final RequestTokenExtractor tokenExtractor;
 
@@ -119,6 +125,10 @@ public abstract class MultiUserEnvironmentInitializationFilter implements Filter
       sessionSubject = extractSubject(token);
       session.setAttribute(CHE_SUBJECT_ATTRIBUTE, sessionSubject);
     } else if (!sessionSubject.getUserId().equals(userId)) {
+      LOG.debug(
+          format(
+              "Invalidating session with mismatched user IDs: old was %s, new is %s.",
+              sessionSubject.getUserId(), userId));
       session.invalidate();
       HttpSession new_session = httpRequest.getSession(true);
       sessionSubject = extractSubject(token);