diff --git a/lib/elastic_apm/transport/connection.rb b/lib/elastic_apm/transport/connection.rb
index b56fa6d79..a3cd1759a 100644
--- a/lib/elastic_apm/transport/connection.rb
+++ b/lib/elastic_apm/transport/connection.rb
@@ -37,7 +37,7 @@ class Connection
 
       def initialize(config)
         @config = config
-        @metadata = JSON.fast_generate(
+        @metadata = JSON.generate(
           Serializers::MetadataSerializer.new(config).build(
             Metadata.new(config)
           )
diff --git a/lib/elastic_apm/transport/worker.rb b/lib/elastic_apm/transport/worker.rb
index 34befc5dc..2b4d0b8a1 100644
--- a/lib/elastic_apm/transport/worker.rb
+++ b/lib/elastic_apm/transport/worker.rb
@@ -87,7 +87,7 @@ def serialize_and_filter(resource)
         # if a filter returns nil, it means skip the event
         return nil if @filters.apply!(serialized) == Filters::SKIP
 
-        JSON.fast_generate(serialized)
+        JSON.generate(serialized)
       rescue Exception
         error format('Failed converting event to JSON: %s', resource.inspect)
         error serialized.inspect
diff --git a/spec/elastic_apm/transport/connection/http_spec.rb b/spec/elastic_apm/transport/connection/http_spec.rb
index d4e973457..7e791bad5 100644
--- a/spec/elastic_apm/transport/connection/http_spec.rb
+++ b/spec/elastic_apm/transport/connection/http_spec.rb
@@ -27,7 +27,7 @@ module Transport
       let(:config) { Config.new(http_compression: false) }
 
       let(:metadata) do
-        JSON.fast_generate(metadata: { service_name: 'Test' })
+        JSON.generate(metadata: { service_name: 'Test' })
       end
 
       let(:url) { 'http://localhost:8200/intake/v2/events' }
diff --git a/spec/elastic_apm/transport/connection_spec.rb b/spec/elastic_apm/transport/connection_spec.rb
index be99951a8..552798aa6 100644
--- a/spec/elastic_apm/transport/connection_spec.rb
+++ b/spec/elastic_apm/transport/connection_spec.rb
@@ -189,7 +189,7 @@ module Transport
 
           before do
             config.api_request_size =
-              "#{JSON.fast_generate(metadata).bytesize - 1}b"
+              "#{JSON.generate(metadata).bytesize - 1}b"
           end
 
           it 'closes requests when reached' do