diff --git a/spec/bundler/support/builders.rb b/spec/bundler/support/builders.rb
index dd61d64c20..b2de94601a 100644
--- a/spec/bundler/support/builders.rb
+++ b/spec/bundler/support/builders.rb
@@ -245,7 +245,7 @@ module Spec
     end
 
     def update_repo(path, build_compact_index: true)
-      if path == gem_repo1 && caller.first.split(" ").last == "`build_repo`"
+      if path == gem_repo1 && caller.first.split(" ").last != "`build_repo'"
         raise "Updating gem_repo1 is unsupported -- use gem_repo2 instead"
       end
       return unless block_given?