diff -up firefox-68.2.0/security/manager/ssl/nsNSSComponent.cpp.old firefox-68.2.0/security/manager/ssl/nsNSSComponent.cpp
--- firefox-68.2.0/security/manager/ssl/nsNSSComponent.cpp.old	2019-10-24 14:20:21.227037984 +0200
+++ firefox-68.2.0/security/manager/ssl/nsNSSComponent.cpp	2019-10-24 14:45:52.769506967 +0200
@@ -996,6 +996,9 @@ void nsNSSComponent::FillTLSVersionRange
     return;
   }
 
+  // Enable TLS 1.3 as our NSS supports it.
+  supported.max = 0x304;
+
   // Clip the defaults by what NSS actually supports to enable
   // working with a system NSS with different ranges.
   rangeOut.min = std::max(rangeOut.min, supported.min);