--- a/devtools/client/locales/en-US/netmonitor.properties
+++ b/devtools/client/locales/en-US/netmonitor.properties
@@ -766,16 +766,20 @@ netmonitor.security.cipherSuite=Cipher s
 # in the security tab describing the key exchange group suite used to secure
 # this connection.
 netmonitor.security.keaGroup=Key Exchange Group:
 
 # LOCALIZATION NOTE (netmonitor.security.keaGroup.none): This is the label
 # displayed in the security tab describing the case when no group was used.
 netmonitor.security.keaGroup.none=none
 
+# LOCALIZATION NOTE (netmonitor.security.keaGroup.custom): This is the label
+# displayed in the security tab describing the case when no group was used.
+netmonitor.security.keaGroup.custom=custom
+
 # LOCALIZATION NOTE (netmonitor.security.keaGroup.unknown): This is the value
 # displayed in the security tab describing an unknown group.
 netmonitor.security.keaGroup.unknown=unknown group
 
 # LOCALIZATION NOTE (netmonitor.security.signatureScheme): This is the label
 # displayed in the security tab describing the signature scheme used by for
 # the server certificate in this connection.
 netmonitor.security.signatureScheme=Signature Scheme:

--- a/devtools/shared/webconsole/network-helper.js
+++ b/devtools/shared/webconsole/network-helper.js
@@ -623,16 +623,19 @@ var NetworkHelper = {
       info.cipherSuite = SSLStatus.cipherName;
 
       // Key exchange group name.
       info.keaGroupName = SSLStatus.keaGroupName;
       // Localise two special values.
       if (info.keaGroupName == "none") {
         info.keaGroupName = L10N.getStr("netmonitor.security.keaGroup.none");
       }
+      if (info.keaGroupName == "custom") {
+        info.keaGroupName = L10N.getStr("netmonitor.security.keaGroup.custom");
+      }
       if (info.keaGroupName == "unknown group") {
         info.keaGroupName = L10N.getStr("netmonitor.security.keaGroup.unknown");
       }
 
       // Certificate signature scheme.
       info.signatureSchemeName = SSLStatus.signatureSchemeName;
       // Localise two special values.
       if (info.signatureSchemeName == "none") {

--- a/security/manager/ssl/nsNSSCallbacks.cpp
+++ b/security/manager/ssl/nsNSSCallbacks.cpp
@@ -847,16 +847,19 @@ getKeaGroupName(uint32_t aKeaGroup)
       groupName = NS_LITERAL_CSTRING("FF 2048");
       break;
     case ssl_grp_ffdhe_3072:
       groupName = NS_LITERAL_CSTRING("FF 3072");
       break;
     case ssl_grp_none:
       groupName = NS_LITERAL_CSTRING("none");
       break;
+    case ssl_grp_ffdhe_custom:
+      groupName = NS_LITERAL_CSTRING("custom");
+      break;
     // All other groups are not enabled in Firefox. See namedGroups in
     // nsNSSIOLayer.cpp.
     default:
       // This really shouldn't happen!
       MOZ_ASSERT_UNREACHABLE("Invalid key exchange group.");
       groupName = NS_LITERAL_CSTRING("unknown group");
   }
   return groupName;