diff --git a/src/keyboard.h b/src/keyboard.h
index 6ef25b88f32..52e6c1d54f5 100644
--- a/src/keyboard.h
+++ b/src/keyboard.h
@@ -26,6 +26,9 @@ extern int num_nonmacro_input_chars;
 /* Nonzero means polling for input is temporarily suppressed.  */
 extern int poll_suppress_count;
 
+/* Nonzero if polling_for_input is actually being used.  */
+extern int polling_for_input;
+
 /* Keymap mapping ASCII function key sequences onto their preferred forms.
    Initialized by the terminal-specific lisp files.  */
 extern Lisp_Object Vfunction_key_map;