diff --git a/src/iperf.h b/src/iperf.h
index e7eb68e..daed1c6 100644
--- a/src/iperf.h
+++ b/src/iperf.h
@@ -270,6 +270,8 @@ struct iperf_test
 #define MB (1024 * 1024)
 #define MAX_TCP_BUFFER (512 * MB)
 #define MAX_BLOCKSIZE MB
+/* Maximum size UDP send is (64K - 1) - IP and UDP header sizes */
+#define MAX_UDP_BLOCKSIZE (65535 - 8 - 20)
 #define MIN_INTERVAL 0.1
 #define MAX_INTERVAL 60.0
 #define MAX_TIME 86400
diff --git a/src/iperf_api.c b/src/iperf_api.c
index 34d97ec..716b881 100644
--- a/src/iperf_api.c
+++ b/src/iperf_api.c
@@ -820,6 +820,11 @@ iperf_parse_arguments(struct iperf_test *test, int argc, char **argv)
 	i_errno = IEBLOCKSIZE;
 	return -1;
     }
+    if (test->protocol->id == Pudp &&
+	blksize > MAX_UDP_BLOCKSIZE) {
+	i_errno = IEUDPBLOCKSIZE;
+	return -1;
+    }
     test->settings->blksize = blksize;
 
     if (!rate_flag)
diff --git a/src/iperf_api.h b/src/iperf_api.h
index 73cba47..0c78985 100644
--- a/src/iperf_api.h
+++ b/src/iperf_api.h
@@ -268,6 +268,7 @@ enum {
     IEFILE = 14,            // -F file couldn't be opened
     IEBURST = 15,           // Invalid burst count. Maximum value = %dMAX_BURST
     IEENDCONDITIONS = 16,   // Only one test end condition (-t, -n, -k) may be specified
+    IEUDPBLOCKSIZE = 20,    // Block size too large. Maximum value = %dMAX_UDP_BLOCKSIZE
     /* Test errors */
     IENEWTEST = 100,        // Unable to create a new test (check perror)
     IEINITTEST = 101,       // Test initialization failed (check perror)
diff --git a/src/iperf_error.c b/src/iperf_error.c
index e1c42ef..1b896e0 100644
--- a/src/iperf_error.c
+++ b/src/iperf_error.c
@@ -110,6 +110,9 @@ iperf_strerror(int i_errno)
         case IEINTERVAL:
             snprintf(errstr, len, "invalid report interval (min = %g, max = %g seconds)", MIN_INTERVAL, MAX_INTERVAL);
             break;
+        case IEUDPBLOCKSIZE:
+            snprintf(errstr, len, "block size too large (maximum = %d bytes)", MAX_UDP_BLOCKSIZE);
+            break;
         case IEMSS:
             snprintf(errstr, len, "TCP MSS too large (maximum = %d bytes)", MAX_MSS);
             break;