diff --git a/test/ares-test-main.cc b/test/ares-test-main.cc
index 9a5a325..09283b9 100644
--- a/test/ares-test-main.cc
+++ b/test/ares-test-main.cc
@@ -1,8 +1,4 @@
-#include <sys/types.h>
-#include <ctype.h>
-#include <errno.h>
-#include <pwd.h>
-#include <iostream>
+#include <stdlib.h>
 
 #include "ares-test.h"
 
@@ -11,6 +7,9 @@ int main(int argc, char* argv[]) {
   for (int ii = 1; ii < argc; ii++) {
     if (strcmp(argv[ii], "-v") == 0) {
       ares::test::verbose = true;
+    } else if ((strcmp(argv[ii], "-p") == 0) && (ii + 1 < argc)) {
+      ii++;
+      ares::test::mock_port = atoi(argv[ii]);
     }
   }
 
diff --git a/test/ares-test.cc b/test/ares-test.cc
index f3cb71f..0bd857c 100644
--- a/test/ares-test.cc
+++ b/test/ares-test.cc
@@ -56,6 +56,7 @@ void ProcessWork(ares_channel channel,
 }  // namespace
 
 bool verbose = false;
+int mock_port = 5300;
 
 unsigned long LibraryTest::fails_ = 0;
 std::map<size_t, int> LibraryTest::size_fails_;
@@ -218,7 +219,7 @@ void MockServer::ProcessRequest(struct sockaddr_storage* addr, int addrlen,
 
 MockChannelOptsTest::MockChannelOptsTest(struct ares_options* givenopts,
                                          int optmask)
-    : server_(5300), channel_(nullptr) {
+  : server_(mock_port), channel_(nullptr) {
   // Set up channel options.
   struct ares_options opts;
   if (givenopts) {
diff --git a/test/ares-test.h b/test/ares-test.h
index 7838a77..a9d5a2e 100644
--- a/test/ares-test.h
+++ b/test/ares-test.h
@@ -21,6 +21,7 @@ typedef unsigned char byte;
 namespace test {
 
 extern bool verbose;
+extern int mock_port;
 
 // Test fixture that ensures library initialization, and allows
 // memory allocations to be failed.