diff --git a/services.cc b/services.cc
index 6631e2d70..493a8475b 100644
--- a/services.cc
+++ b/services.cc
@@ -285,6 +285,8 @@ int addportsfromservmask(const char *mask, u8 *porttbl, int range_type) {
 
   for (i = service_table.begin(); i != service_table.end(); i++) {
     const service_node& current = i->second;
+    if (!current.s_name)
+      continue;
     if (wildtest(mask, current.s_name)) {
       if ((range_type & SCAN_TCP_PORT) && strcmp(current.s_proto, "tcp") == 0) {
         porttbl[current.s_port] |= SCAN_TCP_PORT;
diff --git a/utils.cc b/utils.cc
index 8a8ec2e60..ea39c639e 100644
--- a/utils.cc
+++ b/utils.cc
@@ -81,6 +81,8 @@ extern NmapOps o;
 int wildtest(const char *wild, const char *test) {
   int i;
 
+  assert(wild);
+  assert(test);
   while (*wild != '\0'  ||  *test != '\0') {
     if (*wild == '*') {
       /* --- Deal with multiple asterisks. --- */