--- a/project_files/hwc/rtl/fileio.c	Thu Dec 13 11:03:15 2018 -0500
+++ b/project_files/hwc/rtl/fileio.c	Thu Dec 13 12:12:13 2018 -0500
@@ -186,7 +186,8 @@
  */
 void fpcrtl_blockWrite__vars(File f, const void *buf, Integer count,
         Integer *result) {
-    assert(0);
+    assert(f->record_len > 0);
+    *result = fwrite(buf, f->record_len, count, f->fp);
 }
 
 bool fpcrtl_directoryExists(string255 dir) {