1 files changed, 8 insertions, 0 deletions
diff --git a/lib/bundler/definition.rb b/lib/bundler/definition.rb
index d8aab4fbb4..edaf54a6bf 100644
--- a/lib/bundler/definition.rb
+++ b/lib/bundler/definition.rb
@@ -249,6 +249,14 @@ module Bundler
         return
       end
 
+      locked_major = @locked_bundler_version.segments.first
+      current_major = Gem::Version.create(Bundler::VERSION).segments.first
+
+      if locked_major < current_major
+        Bundler.ui.warn "Warning: the lockfile is being updated to Bundler #{Bundler::VERSION.split('.').first}, " \
+                        "after which you will be unable to return to Bundler #{@locked_bundler_version.segments.first}."
+      end
+
       File.open(file, 'wb'){|f| f.puts(contents) }
     rescue Errno::EACCES
       raise Bundler::InstallError,