diff --git a/uri.c b/uri.c
index 8f684ce1..88a0c2d1 100644
--- a/uri.c
+++ b/uri.c
@@ -72,8 +72,9 @@ coap_split_uri(unsigned char *str_var, size_t len, coap_uri_t *uri) {
   }
 
   /* There might be an additional 's', indicating the secure version: */
-  if ( len && (secure = tolower(*p) == 's') )
-    ++p;
+  if ( len && (secure = tolower(*p) == 's') ) {
+    ++p; --len;
+  }
 
   q = (unsigned char *)"://";
   while (len && *q && tolower(*p) == *q) {