diff --git a/lib/docker.js b/lib/docker.js
index 4750a95..871e16d 100644
--- a/lib/docker.js
+++ b/lib/docker.js
@@ -209,7 +209,7 @@ function dockerContainerStats(containerIDs, callback) {
   // fallback - if only callback is given
   if (util.isFunction(containerIDs) && !callback) {
     callback = containerIDs;
-    containerIDs = '*';
+    containerArray = ['*'];
   } else {
     containerIDs = containerIDs || '*';
     containerIDs = containerIDs.trim().toLowerCase().replace(/,+/g, '|');
@@ -256,7 +256,7 @@ function dockerContainerStats(containerIDs, callback) {
 // --------------------------
 // container stats (for one container)
 
-function dockerContainerStatsSingle(containerID, callback) {
+function dockerContainerStatsSingle(containerID) {
   containerID = containerID || '';
   let result = {
     id: containerID,
@@ -314,11 +314,9 @@ function dockerContainerStatsSingle(containerID, callback) {
             util.noop();
           }
           // }
-          if (callback) { callback(result); }
           resolve(result);
         });
       } else {
-        if (callback) { callback(result); }
         resolve(result);
       }
     });
diff --git a/lib/network.js b/lib/network.js
index 0deabdd..9aee384 100644
--- a/lib/network.js
+++ b/lib/network.js
@@ -463,7 +463,7 @@ function networkStats(ifaces, callback) {
   // fallback - if only callback is given
   if (util.isFunction(ifaces) && !callback) {
     callback = ifaces;
-    ifaces = [getDefaultNetworkInterface()];
+    ifacesArray = [getDefaultNetworkInterface()];
   } else {
     ifaces = ifaces || getDefaultNetworkInterface();
     ifaces = ifaces.trim().toLowerCase().replace(/,+/g, '|');