Index: uspace/lib/c/generic/inet/addr.c
===================================================================
--- uspace/lib/c/generic/inet/addr.c	(revision 1f2b07ab9fedfc54da0cdadeebaa5fb7abc38ca3)
+++ uspace/lib/c/generic/inet/addr.c	(revision 47726b5e33f32673a583b9c6e90c4327cec059fa)
@@ -306,5 +306,5 @@
 		i++;
 
-		if (*cur == '\0')
+		if (*cur == '\0' || *cur == '/')
 			break;
 
@@ -317,4 +317,8 @@
 
 	if (prefix != NULL) {
+		if (*cur != '/')
+			return EINVAL;
+		cur++;
+
 		*prefix = strtoul(cur, &cur, 10);
 		if (*prefix > 32)