diff --git a/lib/modem.js b/lib/modem.js
index 9062eb7..63a4b9b 100644
--- a/lib/modem.js
+++ b/lib/modem.js
@@ -60,7 +60,7 @@ var defaultOpts = function () {
     else {
       opts.pathPrefix = '/';
     }
-    
+
     opts.host = host.hostname;
 
     if (process.env.DOCKER_CERT_PATH) {
@@ -248,10 +248,13 @@ Modem.prototype.dial = function (options, callback) {
 
 Modem.prototype.getSocketPath = function () {
   if (!this.socketPath) return;
+  if (this.socketPathCache) return Promise.resolve(this.socketPathCache);
 
   var socketPathValue = typeof this.socketPath === 'function'
     ? this.socketPath() : this.socketPath;
 
+  this.socketPathCache = socketPathValue;
+
   return Promise.resolve(socketPathValue);
 }
 
diff --git a/test/modem_test.js b/test/modem_test.js
index d12e5a4..961c438 100644
--- a/test/modem_test.js
+++ b/test/modem_test.js
@@ -83,6 +83,26 @@ describe('Modem', function () {
     });
   });
 
+  it('should use custom socketPath function once', function () {
+    process.env.DOCKER_HOST = 'unix://';
+
+    var count = 0;
+
+    var modem = new Modem();
+    modem.socketPath = function() {
+      assert(++count === 1);
+      return 'testpath';
+    }
+    modem.getSocketPath().then((socketPath) => {
+      assert.ok(socketPath);
+      assert.ok('testpath');
+    });
+    return modem.getSocketPath().then((socketPath) => {
+      assert.ok(socketPath);
+      assert.ok('testpath');
+    });
+  });
+
   it('should interpret DOCKER_HOST=tcp://N.N.N.N:2376 as https', function () {
     process.env.DOCKER_HOST = 'tcp://192.168.59.103:2376';