diff --git a/ChangeLog b/ChangeLog
index bdb3a30c..141b4ed8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2021-11-07  Joerg Wunsch <j.gnu@uriah.heep.sax.de>
+
+	bug #50517: Reading fails if "immediate mode" for output file format is selected - fileio: invalid operation=1
+	* update.c (do_op): refuse to write to "immediate format" argument
+
 2021-11-07  Joerg Wunsch <j.gnu@uriah.heep.sax.de>
 
 	Submitted by Martin Thierer:
diff --git a/NEWS b/NEWS
index 22f24697..405aa05c 100644
--- a/NEWS
+++ b/NEWS
@@ -64,6 +64,7 @@ Current:
     bug #55734: USBtiny programming of ATmega328p broken by Patch #9278
     bug #58495: Add atmega324pb support to avrdude.conf.in
     bug #60863: avrftdi programming error probably caused by multiple, consecutive empty pages
+    bug #50517: Reading fails if "immediate mode" for output file format is selected - fileio: invalid operation=1
 
   * Patches:
     patch #9482: Add support for UPDI and AVR8X
diff --git a/update.c b/update.c
index bf6749d7..95e1028f 100644
--- a/update.c
+++ b/update.c
@@ -230,6 +230,12 @@ int do_op(PROGRAMMER * pgm, struct avrpart * p, UPDATE * upd, enum updateflags f
     /*
      * read out the specified device memory and write it to a file
      */
+    if (upd->format == FMT_IMM) {
+      avrdude_message(MSG_INFO,
+                      "%s: Invalid file format 'immediate' for output\n",
+                      progname, upd->filename);
+      return -1;
+    }
     if (quell_progress < 2) {
       avrdude_message(MSG_INFO, "%s: reading %s memory:\n",
             progname, mem->desc);