diff --git a/lib/docker.js b/lib/docker.js
index 253a4b0..b6a61ae 100644
--- a/lib/docker.js
+++ b/lib/docker.js
@@ -110,7 +110,7 @@ exports.dockerContainers = dockerContainers;
 // --------------------------
 // helper functions for calculation of docker stats
 
-function docker_calcCPUPercent(cpu_stats, id) {
+function docker_calcCPUPercent(cpu_stats, precpu_stats) {
   /**
    * @namespace
    * @property {object}  cpu_usage
@@ -122,16 +122,13 @@ function docker_calcCPUPercent(cpu_stats, id) {
 
   let cpuPercent = 0.0;
   // calculate the change for the cpu usage of the container in between readings
-  let cpuDelta = cpu_stats.cpu_usage.total_usage - (_docker_container_stats[id] && _docker_container_stats[id].prev_CPU ? _docker_container_stats[id].prev_CPU : 0);
+  let cpuDelta = cpu_stats.cpu_usage.total_usage - precpu_stats.cpu_usage.total_usage;
   // calculate the change for the entire system between readings
-  let systemDelta = cpu_stats.system_cpu_usage - (_docker_container_stats[id] && _docker_container_stats[id].prev_system ? _docker_container_stats[id].prev_system : 0);
+  let systemDelta = cpu_stats.system_cpu_usage - precpu_stats.system_cpu_usage;
 
   if (systemDelta > 0.0 && cpuDelta > 0.0) {
     cpuPercent = (cpuDelta / systemDelta) * cpu_stats.cpu_usage.percpu_usage.length * 100.0;
   }
-  if (!_docker_container_stats[id]) _docker_container_stats[id] = {};
-  _docker_container_stats[id].prev_CPU = cpu_stats.cpu_usage.total_usage;
-  _docker_container_stats[id].prev_system = cpu_stats.system_cpu_usage;
 
   return cpuPercent;
 }
@@ -235,7 +232,7 @@ function dockerContainerStats(containerID, callback) {
               result.mem_usage = (stats.memory_stats && stats.memory_stats.usage ? stats.memory_stats.usage : 0);
               result.mem_limit = (stats.memory_stats && stats.memory_stats.limit ? stats.memory_stats.limit : 0);
               result.mem_percent = (stats.memory_stats && stats.memory_stats.usage && stats.memory_stats.limit ? stats.memory_stats.usage / stats.memory_stats.limit * 100.0 : 0);
-              result.cpu_percent = (stats.cpu_stats ? docker_calcCPUPercent(stats.cpu_stats, containerID) : 0);
+              result.cpu_percent = (stats.cpu_stats && stats.precpu_stats ? docker_calcCPUPercent(stats.cpu_stats, stats.precpu_stats) : 0);
               result.pids = (stats.pids_stats && stats.pids_stats.current ? stats.pids_stats.current : 0);
               if (stats.networks) result.netIO = docker_calcNetworkIO(stats.networks);
               if (stats.blkio_stats) result.blockIO = docker_calcBlockIO(stats.blkio_stats);
@@ -283,7 +280,7 @@ function dockerContainerProcesses(containerID, callback) {
            **/
           try {
             if (data && data.Titles && data.Processes) {
-              let titles = data.Titles.map(function(value) {
+              let titles = data.Titles.map(function (value) {
                 return value.toUpperCase();
               });
               let pos_pid = titles.indexOf('PID');