diff --git a/ChangeLog b/ChangeLog
index 7700b87f56..cdf5dca809 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Tue Jul 26 18:55:55 2016  Koichi Sasada  <ko1@atdot.net>
+
+	* gc.c (gc_mark): add `inline' explicitly.
+	  I expected to inline this function implicitly at the loop
+	  (ex: marking T_ARRAY objects) but sometimes it remains as
+	  normal call.
+
 Tue Jul 26 16:33:16 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* enc/windows_1257.c, test/ruby/enc/test_case_comprehensive.rb:
diff --git a/gc.c b/gc.c
index bc55f78a50..fd0566c4ca 100644
--- a/gc.c
+++ b/gc.c
@@ -853,7 +853,7 @@ static void gc_sweep_rest(rb_objspace_t *objspace);
 static void gc_sweep_continue(rb_objspace_t *objspace, rb_heap_t *heap);
 #endif
 
-static void gc_mark(rb_objspace_t *objspace, VALUE ptr);
+static inline void gc_mark(rb_objspace_t *objspace, VALUE ptr);
 static void gc_mark_ptr(rb_objspace_t *objspace, VALUE ptr);
 static void gc_mark_maybe(rb_objspace_t *objspace, VALUE ptr);
 static void gc_mark_children(rb_objspace_t *objspace, VALUE ptr);
@@ -4347,7 +4347,7 @@ gc_mark_ptr(rb_objspace_t *objspace, VALUE obj)
     }
 }
 
-static void
+static inline void
 gc_mark(rb_objspace_t *objspace, VALUE obj)
 {
     if (!is_markable_object(objspace, obj)) return;