diff --git a/src/main/java/tomcat/request/session/redis/SessionHandlerValve.java b/src/main/java/tomcat/request/session/redis/SessionHandlerValve.java
index aa891bc..7d6a347 100644
--- a/src/main/java/tomcat/request/session/redis/SessionHandlerValve.java
+++ b/src/main/java/tomcat/request/session/redis/SessionHandlerValve.java
@@ -31,7 +31,9 @@ public class SessionHandlerValve extends ValveBase {
             LOGGER.error("Error processing request", ex);
             throw new BackendException();
         } finally {
-            this.manager.afterRequest();
+            if (this.manager != null) {
+                this.manager.afterRequest();
+            }
         }
     }
 }
diff --git a/src/main/java/tomcat/request/session/redis/SingleSignOnValve.java b/src/main/java/tomcat/request/session/redis/SingleSignOnValve.java
index 49f58c1..cd4bae8 100644
--- a/src/main/java/tomcat/request/session/redis/SingleSignOnValve.java
+++ b/src/main/java/tomcat/request/session/redis/SingleSignOnValve.java
@@ -225,7 +225,9 @@ public class SingleSignOnValve extends SingleSignOn {
 
     /** To set session manager. */
     void setSessionManager(Manager manager) {
-        this.manager = (SessionManager) manager;
+        if (manager != null) {
+            this.manager = (SessionManager) manager;
+        }
     }
 
     /** To expire session. */