diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 7e068c7..8b1db92 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -3315,8 +3315,8 @@
 
     msg = ssl->in_msg + mbedtls_ssl_hs_hdr_len( ssl );
 
-    lifetime = ( msg[0] << 24 ) | ( msg[1] << 16 ) |
-               ( msg[2] <<  8 ) | ( msg[3]       );
+    lifetime = ( ((uint32_t) msg[0]) << 24 ) | ( msg[1] << 16 ) |
+               ( msg[2] << 8 ) | ( msg[3] );
 
     ticket_len = ( msg[4] << 8 ) | ( msg[5] );