diff --git a/handler/src/main/java/io/netty/handler/ssl/JettyNpnSslSession.java b/handler/src/main/java/io/netty/handler/ssl/JettyNpnSslSession.java
index b05866f174..f4da3da1d5 100644
--- a/handler/src/main/java/io/netty/handler/ssl/JettyNpnSslSession.java
+++ b/handler/src/main/java/io/netty/handler/ssl/JettyNpnSslSession.java
@@ -34,6 +34,9 @@ final class JettyNpnSslSession implements SSLSession {
     }
 
     void setApplicationProtocol(String applicationProtocol) {
+        if (applicationProtocol != null) {
+            applicationProtocol = applicationProtocol.replace(':', '_');
+        }
         this.applicationProtocol = applicationProtocol;
     }
 
diff --git a/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java b/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java
index 8d27bfa042..677df6c9d2 100644
--- a/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java
+++ b/handler/src/main/java/io/netty/handler/ssl/OpenSslEngine.java
@@ -808,7 +808,7 @@ public final class OpenSslEngine extends SSLEngine {
                 if (applicationProtocol == null) {
                     applicationProtocol = fallbackApplicationProtocol;
                 }
-                this.applicationProtocol = applicationProtocol;
+                this.applicationProtocol = applicationProtocol.replace(':', '_');
                 return FINISHED;
             }