diff --git a/Gemfile.lock b/Gemfile.lock
index eec4ab4..dc6adf3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    bundler-multilock (1.1.0)
+    bundler-multilock (1.1.1)
       bundler (~> 2.4.19)
 
 GEM
diff --git a/lib/bundler/multilock.rb b/lib/bundler/multilock.rb
index 1ff2830..6a79c28 100644
--- a/lib/bundler/multilock.rb
+++ b/lib/bundler/multilock.rb
@@ -460,7 +460,7 @@ def write_lockfile(lockfile_definition, lockfile, install:, dependency_changes:
             definition.send(:source_map).locked_specs.each do |spec|
               next if spec.match_platform(Bundler.local_platform)
 
-              spec.source.specs.add(spec)
+              spec.source.specs << spec
             end
             definition.resolve_with_cache!
           rescue GemNotFound, SolveFailure
diff --git a/lib/bundler/multilock/version.rb b/lib/bundler/multilock/version.rb
index a118e51..11531c7 100644
--- a/lib/bundler/multilock/version.rb
+++ b/lib/bundler/multilock/version.rb
@@ -2,6 +2,6 @@
 
 module Bundler
   module Multilock
-    VERSION = "1.1.0"
+    VERSION = "1.1.1"
   end
 end