diff --git a/tool/jt.rb b/tool/jt.rb
index 870d88edcb..0a6e4c367b 100755
--- a/tool/jt.rb
+++ b/tool/jt.rb
@@ -152,13 +152,16 @@ module Utilities
   end
 
   def find_mx
-    if which('mx')
-      'mx'
+    if ENV.key?("MX_GIT_CACHE_DIR")
+      "mx-internal"
     else
-      mx_repo = find_or_clone_repo("https://github.com/graalvm/mx.git")
-      "#{mx_repo}/mx"
+      if which('mx')
+        'mx'
+      else
+        mx_repo = find_or_clone_repo("https://github.com/graalvm/mx.git")
+        "#{mx_repo}/mx"
+      end
     end
-  end
 
   def find_launcher(use_native)
     if use_native
@@ -444,8 +447,8 @@ module Commands
           --no-sforceimports                         do not run sforceimports before building
           parser                                     build the parser
           options                                    build the options
-          graalvm                                    build a minimal JVM-only GraalVM containing only TruffleRuby, 
-                                                     available by default in mxbuild/truffleruby-jvm, 
+          graalvm                                    build a minimal JVM-only GraalVM containing only TruffleRuby,
+                                                     available by default in mxbuild/truffleruby-jvm,
                                                      the Ruby is symlinked into rbenv or chruby if available
               --graal      include the GraalVM Compiler in the build
               --native     build native ruby image as well, available in mxbuild/truffleruby-native
@@ -491,7 +494,7 @@ module Commands
       jt test compiler                               run compiler tests
       jt test integration [TESTS]                    run integration tests
       jt test bundle [--jdebug]                      tests using bundler
-      jt test gems [TESTS]                           tests using gems 
+      jt test gems [TESTS]                           tests using gems
       jt test ecosystem [TESTS]                      tests using the wider ecosystem such as bundler, Rails, etc
       jt test cexts [--no-openssl] [--no-gems] [test_names...]
                                                      run C extension tests (set GEM_HOME)