diff --git a/beakerx/beakerx/runtime.py b/beakerx/beakerx/runtime.py
index 30d786c856..eceaef9889 100644
--- a/beakerx/beakerx/runtime.py
+++ b/beakerx/beakerx/runtime.py
@@ -619,5 +619,6 @@ def get_context_session():
     kernel = get_ipython().kernel
     # if subkernel get session from extra start parameters
     if len(kernel.parent.argv) == 3:
-        return json.loads(kernel.parent.argv[2])['contextId']
+        context_json = base64.b64decode(kernel.parent.argv[2]).decode('UTF-8')
+        return json.loads(context_json)['contextId']
     return kernel.session.session
diff --git a/beakerx/beakerx_magics/kernel_magic.py b/beakerx/beakerx_magics/kernel_magic.py
index ff3b50a9b7..6a66e2896a 100644
--- a/beakerx/beakerx_magics/kernel_magic.py
+++ b/beakerx/beakerx_magics/kernel_magic.py
@@ -17,6 +17,7 @@
 from jupyter_client.manager import KernelManager
 from ipykernel.zmqshell import ZMQInteractiveShell
 import atexit
+import base64
 import json
 import logging
 import os
@@ -38,7 +39,7 @@ def __init__(self, shell):
     def start(self, kernel_name):
         self.km = KernelManager()
         self.km.kernel_name = kernel_name
-        self.km.start_kernel(extra_arguments=[self._context_as_string()])
+        self.km.start_kernel(extra_arguments=[self._context_base64()])
         atexit.register(self.stop_kernel)
         self.kc = self.km.client()
         self.kc.start_channels()
@@ -85,11 +86,12 @@ def pass_message(self, msg_raw):
                 # don't create the list of keys if debug messages aren't enabled
                 self.log.debug("Current comms: %s", list(self.comms.keys()))
 
-    def _context_as_string(self):
-        return json.dumps({
+    def _context_base64(self):
+        context_json = json.dumps({
             'port': os.environ["BEAKERX_AUTOTRANSLATION_PORT"],
             'contextId': get_ipython().kernel.session.session,
         })
+        return base64.b64encode(context_json.encode('utf-8')).decode()
 
 
 def comm_msg(stream, ident, msg):
diff --git a/kernel/base/src/main/java/com/twosigma/beakerx/kernel/KernelConfigurationFile.java b/kernel/base/src/main/java/com/twosigma/beakerx/kernel/KernelConfigurationFile.java
index 8fee3103fb..6a9632158c 100644
--- a/kernel/base/src/main/java/com/twosigma/beakerx/kernel/KernelConfigurationFile.java
+++ b/kernel/base/src/main/java/com/twosigma/beakerx/kernel/KernelConfigurationFile.java
@@ -19,9 +19,11 @@
 import com.twosigma.beakerx.message.MessageSerializer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import py4j.Base64;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.UnsupportedEncodingException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.Map;
@@ -44,7 +46,12 @@ public KernelConfigurationFile(final String[] args) {
     }
     this.config = getConfig(args[0]);
     if (args.length == 2) {
-      String contextAsJson = args[1];
+      String contextAsJson = null;
+      try {
+        contextAsJson = new String(Base64.decode(args[1]), "UTF-8");
+      } catch (UnsupportedEncodingException e) {
+        e.printStackTrace();
+      }
       this.context = Optional.of(contextAsJson);
     }
   }
diff --git a/kernel/base/src/main/java/com/twosigma/beakerx/kernel/MagicKernelManager.java b/kernel/base/src/main/java/com/twosigma/beakerx/kernel/MagicKernelManager.java
index 812615a496..dcba252a06 100644
--- a/kernel/base/src/main/java/com/twosigma/beakerx/kernel/MagicKernelManager.java
+++ b/kernel/base/src/main/java/com/twosigma/beakerx/kernel/MagicKernelManager.java
@@ -19,6 +19,7 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.twosigma.beakerx.message.Header;
 import com.twosigma.beakerx.message.Message;
+import org.apache.commons.codec.binary.Base64;
 import py4j.ClientServer;
 import py4j.GatewayServer;
 
@@ -28,6 +29,7 @@
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.ServerSocket;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -84,7 +86,7 @@ protected String[] getPy4jCommand() {
             "--port", port == null ? DEFAULT_PORT : String.valueOf(port),
             "--pyport", pythonPort == null ? DEFAULT_PYTHON_PORT : String.valueOf(pythonPort),
             "--kernel", kernelName,
-            "--context", this.context
+            "--context", Base64.encodeBase64String(this.context.getBytes(StandardCharsets.UTF_8))
     };
   }