diff --git a/src/newgrf.cpp b/src/newgrf.cpp
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -47,6 +47,7 @@
 #include "newgrf_industries.h"
 #include "table/landscape_sprite.h"
 #include "gfxinit.h"
+#include "fios.h"
 
 /* TTDPatch extended GRF format codec
  * (c) Petr Baudis 2004 (GPL'd)
@@ -5421,6 +5422,15 @@ void LoadNewGRFFile(GRFConfig *config, u
 		if (stage == GLS_ACTIVATION && config->status != GCS_INITIALISED) return;
 	}
 
+	if (file_index > LAST_GRF_SLOT) {
+		DEBUG(grf, 0, "'%s' is not loaded as the maximum number of GRFs has been reached", filename);
+		config->status = GCS_DISABLED;
+		config->error  = CallocT<GRFError>(1);
+		config->error->severity = STR_NEWGRF_ERROR_MSG_FATAL;
+		config->error->message  = STR_NEWGRF_ERROR_TOO_MANY_NEWGRFS_LOADED;
+		return;
+	}
+
 	FioOpenFile(file_index, filename);
 	_file_index = file_index; // XXX