diff --git a/src/gc.c b/src/gc.c
index 8eda76b26..e87ed3f06 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1589,5 +1589,5 @@ gc_test(mrb_state *mrb, mrb_value self)
   test_incremental_sweep_phase();
   return mrb_nil_value();
 }
-#endif
-#endif
+#endif  /* GC_DEBUG */
+#endif  /* GC_TEST */
diff --git a/src/mrb_throw.h b/src/mrb_throw.h
index 859729be6..3c7407a8d 100644
--- a/src/mrb_throw.h
+++ b/src/mrb_throw.h
@@ -38,4 +38,4 @@ struct mrb_jmpbuf {
 #endif
 };
 
-#endif
+#endif  /* MRB_THROW_H */
diff --git a/src/re.h b/src/re.h
index a1fe75aab..ee2638b22 100644
--- a/src/re.h
+++ b/src/re.h
@@ -9,4 +9,4 @@
 
 #define REGEXP_CLASS          "Regexp"
 
-#endif
+#endif  /* RE_H */