diff --git a/libguile/debug.c b/libguile/debug.c
index 6a42d42e6..9fbc950a3 100644
--- a/libguile/debug.c
+++ b/libguile/debug.c
@@ -385,6 +385,8 @@ scm_make_debugobj (frame)
 
 
 
+/* Undocumented debugging procedure */
+#ifdef GUILE_DEBUG
 SCM_PROC (s_debug_hang, "debug-hang", 0, 1, 0, scm_debug_hang);
 
 SCM
@@ -395,6 +397,7 @@ scm_debug_hang (obj)
   while (!go) ;
   return SCM_UNSPECIFIED;
 }
+#endif