--- c-kermit/ckucmd.c	2020-04-25 13:43:15.000000000 -0700
+++ c-kermit-fix/ckucmd.c	2020-07-24 11:43:43.436751064 -0700
@@ -7575,9 +7575,10 @@
 
 /* Here we must look inside the stdin buffer - highly platform dependent */
 
-#ifdef _IO_file_flags			/* Linux */
+#if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
+    /* glibc and similar libraries */
     x = (int) ((stdin->_IO_read_end) - (stdin->_IO_read_ptr));
-    debug(F101,"cmdconchk _IO_file_flags","",x);
+    debug(F101,"cmdconchk glibc-style","",x);
 #else  /* _IO_file_flags */
 #ifdef USE_FILE_CNT			/* Traditional */
 #ifdef VMS