diff --git a/pjlib/src/pj/sock_common.c b/pjlib/src/pj/sock_common.c
index 4a1e795..ec649e6 100644
--- a/pjlib/src/pj/sock_common.c
+++ b/pjlib/src/pj/sock_common.c
@@ -900,7 +900,7 @@
 		    unsigned k;
 
 		    for (k=0; k<16; ++k) {
-			am[k] = (a[k] & pm[k]) & 0xFF;
+			am[k] = (pj_uint8_t)((a[k] & pm[k]) & 0xFF);
 		    }
 
 		    if (pj_memcmp(am, pa, 16)==0) {