diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 0b340d5..e9523ce 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -50,7 +50,7 @@
 #endif
 
 #define SERVER_NAME "localhost"
-#define SERVER_PORT 11999
+#define SERVER_PORT "11999"
 
 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) ||     \
     !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) ||  \
@@ -134,7 +134,7 @@
     /*
      * 3. Initiate the connection
      */
-    mbedtls_printf( "\n  . Connecting to tcp/%s/%d", SERVER_NAME,
+    mbedtls_printf( "\n  . Connecting to tcp/%s/%s", SERVER_NAME,
                                              SERVER_PORT );
     fflush( stdout );
 
diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index 8fda29f..30abaa8 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -49,7 +49,7 @@
 #include <string.h>
 #endif
 
-#define SERVER_PORT 11999
+#define SERVER_PORT "11999"
 #define PLAINTEXT "==Hello there!=="
 
 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) ||     \