diff --git a/src/iperf.h b/src/iperf.h
index dc3c0d1df..cf7c0aa36 100644
--- a/src/iperf.h
+++ b/src/iperf.h
@@ -294,7 +294,7 @@ struct iperf_test
     int       bind_port;                        /* --cport option */
     int       server_port;
     int       omit;                             /* duration of omit period (-O flag) */
-    int       duration;                         /* total duration of test (-t flag) */
+    uint32_t  duration;                         /* total duration of test (-t flag) */
     char     *diskfile_name;			/* -F option */
     int       affinity, server_affinity;	/* -A option */
 #if defined(HAVE_CPUSET_SETAFFINITY)