diff --git a/lib/appsignal/transaction.rb b/lib/appsignal/transaction.rb
index <HASH>..<HASH> 100644
--- a/lib/appsignal/transaction.rb
+++ b/lib/appsignal/transaction.rb
@@ -137,7 +137,7 @@ module Appsignal
         Appsignal.logger.debug("Setting http queue start: #{env_var}")
         value = env_var.tr('^0-9', '')
         unless value.empty?
-          @queue_start = value.to_f / 1000
+          @queue_start = value.to_f / 1000.0
         end
       end
     end
Make sure we don't use resolution in http queue time calculation