diff --git a/libguile/gc.c b/libguile/gc.c
index 0cf3a0873..16de3d978 100644
--- a/libguile/gc.c
+++ b/libguile/gc.c
@@ -441,7 +441,7 @@ scm_igc (what)
   SCM_THREAD_CRITICAL_SECTION_START;
 #endif
 
-  // fprintf (stderr, "gc: %s\n", what);
+  /* fprintf (stderr, "gc: %s\n", what); */
 
   scm_gc_start (what);
   if (!scm_stack_base || scm_block_gc)