diff --git a/appsignal-sourcemap.gemspec b/appsignal-sourcemap.gemspec
index 4bca877..9ddb7c1 100644
--- a/appsignal-sourcemap.gemspec
+++ b/appsignal-sourcemap.gemspec
@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.files = Dir["lib/**/*", "README.md"]
 
   spec.add_dependency "rails", ">= 6.1", "< 8.0"
-  spec.add_dependency "appsignal", "~> 3.0"
+  spec.add_dependency "appsignal", "< 5.0"
   spec.add_dependency "parallel", "~> 1.0"
 
   spec.add_development_dependency "standard"
diff --git a/lib/appsignal/sourcemap/version.rb b/lib/appsignal/sourcemap/version.rb
index ea2392b..2520129 100644
--- a/lib/appsignal/sourcemap/version.rb
+++ b/lib/appsignal/sourcemap/version.rb
@@ -2,6 +2,6 @@
 
 module Appsignal
   module Sourcemap
-    VERSION = "1.1.1.develop"
+    VERSION = "1.2.1.develop"
   end
 end