diff --git a/runtime/doc/tags b/runtime/doc/tags
index 706970f17a..39f279d361 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -10688,6 +10688,7 @@ termdebug-starting	terminal.txt	/*termdebug-starting*
 termdebug-stepping	terminal.txt	/*termdebug-stepping*
 termdebug-timeout	terminal.txt	/*termdebug-timeout*
 termdebug-variables	terminal.txt	/*termdebug-variables*
+termdebug_contributing	terminal.txt	/*termdebug_contributing*
 termdebug_disasm_window	terminal.txt	/*termdebug_disasm_window*
 termdebug_evaluate_in_popup	terminal.txt	/*termdebug_evaluate_in_popup*
 termdebug_map_K	terminal.txt	/*termdebug_map_K*
diff --git a/runtime/doc/terminal.txt b/runtime/doc/terminal.txt
index 637277ab59..593dec77c7 100644
--- a/runtime/doc/terminal.txt
+++ b/runtime/doc/terminal.txt
@@ -1,4 +1,4 @@
-*terminal.txt*	For Vim version 9.1.  Last change: 2024 Nov 10
+*terminal.txt*	For Vim version 9.1.  Last change: 2024 Nov 19
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1737,4 +1737,23 @@ This can also be used in a "one-shot" manner: >
 	  let g:termdebug_config['evaluate_in_popup'] = v:false
 	endfunc
 <
+
+Contributing ~
+						*termdebug_contributing*
+Contributions for termdebug improvements are welcome.
+However, it is fairly common that during the development process you need some
+mechanisms like `echo` statements (or similar) to help you in your job.
+For this reason, you can set: >
+    let g:termdebug_config['debug'] = true
+<
+This sets the `DEBUG` variable to `true` in the source code that you can use
+within the source code. An example of its usage follows: >
+    if exists('g:termdebug_loaded')
+      if DEBUG
+	Echoerr('Termdebug already loaded.')
+      endif
+      finish
+    endif
+<
+
  vim:tw=78:ts=8:noet:ft=help:norl:
diff --git a/runtime/pack/dist/opt/termdebug/plugin/termdebug.vim b/runtime/pack/dist/opt/termdebug/plugin/termdebug.vim
index 6f1f4b5227..9fbf3b7f69 100644
--- a/runtime/pack/dist/opt/termdebug/plugin/termdebug.vim
+++ b/runtime/pack/dist/opt/termdebug/plugin/termdebug.vim
@@ -4,7 +4,7 @@ vim9script
 
 # Author: Bram Moolenaar
 # Copyright: Vim license applies, see ":help license"
-# Last Change: 2024 Jul 04
+# Last Change: 2024 Nov 19
 # Converted to Vim9: Ubaldo Tiberi <ubaldo.tiberi@gmail.com>
 
 # WORK IN PROGRESS - The basics works stable, more to come
@@ -38,6 +38,11 @@ vim9script
 # The communication with gdb uses GDB/MI.  See:
 # https://sourceware.org/gdb/current/onlinedocs/gdb/GDB_002fMI.html
 
+var DEBUG = false
+if exists('g:termdebug_config')
+  DEBUG = get(g:termdebug_config, 'debug', false)
+endif
+
 def Echoerr(msg: string)
   echohl ErrorMsg | echom $'[termdebug] {msg}' | echohl None
 enddef
@@ -49,7 +54,9 @@ enddef
 # Variables to keep their status among multiple instances of Termdebug
 # Avoid to source the script twice.
 if exists('g:termdebug_loaded')
-  Echoerr('Termdebug already loaded.')
+  if DEBUG
+    Echoerr('Termdebug already loaded.')
+  endif
   finish
 endif
 g:termdebug_loaded = true
diff --git a/src/testdir/test_termdebug.vim b/src/testdir/test_termdebug.vim
index 17e1d897a3..0acdab1a50 100644
--- a/src/testdir/test_termdebug.vim
+++ b/src/testdir/test_termdebug.vim
@@ -57,6 +57,8 @@ endfunction
 
 packadd termdebug
 
+" should be the first test to run, since it validates the window layout with
+" win ids
 func Test_termdebug_basic()
   let bin_name = 'XTD_basic'
   let src_name = bin_name .. '.c'
@@ -620,4 +622,22 @@ function Test_termdebug_config_types()
   unlet g:termdebug_config
 endfunction
 
+function Test_termdebug_config_debug()
+  let s:error_message = '\[termdebug\] Termdebug already loaded'
+
+  " USER mode: No error message shall be displayed
+  packadd termdebug
+  call assert_true(execute('messages') !~ s:error_message)
+
+  " DEBUG mode: Error message shall now be displayed
+  let g:termdebug_config = {}
+  let g:termdebug_config['debug'] = 1
+  packadd termdebug
+  call assert_true(execute('messages') =~ s:error_message)
+
+  unlet g:termdebug_config
+  unlet g:termdebug_loaded
+  " Revert DEBUG mode, by reloading the plugin
+  source $VIMRUNTIME/pack/dist/opt/termdebug/plugin/termdebug.vim
+endfunction
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 422633aa6c..6b263ea04e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    878,
 /**/
     877,
 /**/