diff --git a/source/src/master.cpp b/source/src/master.cpp
index 6a0485f4..577d363a 100644
--- a/source/src/master.cpp
+++ b/source/src/master.cpp
@@ -571,7 +571,7 @@ int main(int argc, char **argv)
     const char *dir = "", *ip = AC_MASTER_URI;
     int port = AC_MASTER_PORT;
     if(argc>=2) dir = argv[1];
-    if(argc>=3) port = atoi(argv[2]);
+    if(argc>=3 && argv[2][0]) port = atoi(argv[2]);
     if(argc>=4) ip = argv[3][0] ? argv[3] : NULL;
     defformatstring(logname)("%smaster.log", dir);
     defformatstring(cfgname)("%smaster.cfg", dir);
diff --git a/source/src/serverfiles.h b/source/src/serverfiles.h
index 7e1e9db0..e35efa37 100644
--- a/source/src/serverfiles.h
+++ b/source/src/serverfiles.h
@@ -288,6 +288,7 @@ struct servermaprot : serverconfigfile
             return -1;
         }
 #endif
+        if(configsets.empty()) fatal("maprot unavailable");
         int n = numclients();
         int csl = configsets.length();
         int ccs = curcfgset;