diff --git a/class.c b/class.c
index 597f6bd618..cf25ad2a0c 100644
--- a/class.c
+++ b/class.c
@@ -1712,6 +1712,8 @@ singleton_class_of(VALUE obj)
 	  case T_STRING:
 	    if (FL_TEST_RAW(obj, RSTRING_FSTR)) goto no_singleton;
 	    break;
+          default:
+            break;
 	}
     }
 
diff --git a/compile.c b/compile.c
index a894741e09..bd249a57c0 100644
--- a/compile.c
+++ b/compile.c
@@ -8677,6 +8677,8 @@ opobj_inspect(VALUE obj)
 	  case T_ARRAY:
 	    obj = rb_ary_dup(obj);
 	    break;
+          default:
+            break;
 	}
     }
     return rb_inspect(obj);
diff --git a/eval.c b/eval.c
index 8b1897cc0b..0102171205 100644
--- a/eval.c
+++ b/eval.c
@@ -468,6 +468,8 @@ rb_class_modify_check(VALUE klass)
 		  case T_CLASS:
 		    desc = "Class";
 		    break;
+                  default:
+                    break;
 		}
 	    }
 	}
diff --git a/ext/objspace/objspace_dump.c b/ext/objspace/objspace_dump.c
index d753b48a80..7dd0731c43 100644
--- a/ext/objspace/objspace_dump.c
+++ b/ext/objspace/objspace_dump.c
@@ -135,6 +135,7 @@ obj_type(VALUE obj)
 	CASE_TYPE(NODE);
 	CASE_TYPE(ZOMBIE);
 #undef CASE_TYPE
+      default: break;
     }
     return "UNKNOWN";
 }
@@ -315,6 +316,9 @@ dump_object(VALUE obj, struct dump_config *dc)
       case T_ZOMBIE:
 	dump_append(dc, "}\n");
 	return;
+
+      default:
+        break;
     }
 
     rb_objspace_reachable_objects_from(obj, reachable_object_i, dc);
diff --git a/gc.c b/gc.c
index eb49f044c9..a1b8dcf48c 100644
--- a/gc.c
+++ b/gc.c
@@ -2594,6 +2594,8 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
       case T_FALSE:
 	rb_bug("obj_free() called for broken object");
 	break;
+      default:
+        break;
     }
 
     if (FL_TEST(obj, FL_EXIVAR)) {
@@ -3564,6 +3566,8 @@ rb_objspace_call_finalizer(rb_objspace_t *objspace)
                     make_io_zombie(objspace, vp);
 		}
 		break;
+              default:
+                break;
 	    }
             if (poisoned) {
                 GC_ASSERT(BUILTIN_TYPE(vp) == T_NONE);
@@ -3634,6 +3638,8 @@ is_live_object(rb_objspace_t *objspace, VALUE ptr)
       case T_NONE:
       case T_ZOMBIE:
 	return FALSE;
+      default:
+        break;
     }
 
     if (!is_garbage_object(objspace, ptr)) {
@@ -4588,6 +4594,9 @@ push_mark_stack(mark_stack_t *stack, VALUE data)
       case T_NODE:
 	UNEXPECTED_NODE(push_mark_stack);
         break;
+
+      default:
+        break;
     }
 
     if (stack->index == stack->limit) {
@@ -5397,6 +5406,9 @@ gc_mark_children(rb_objspace_t *objspace, VALUE obj)
       case T_IMEMO:
 	gc_mark_imemo(objspace, obj);
 	return;
+
+      default:
+        break;
     }
 
     gc_mark(objspace, any->as.basic.klass);
diff --git a/iseq.c b/iseq.c
index 7c888f5a16..04887351e7 100644
--- a/iseq.c
+++ b/iseq.c
@@ -68,6 +68,8 @@ obj_resurrect(VALUE obj)
           case T_HASH:
             obj = rb_hash_resurrect(obj);
             break;
+          default:
+	    break;
 	}
     }
     return obj;
diff --git a/numeric.c b/numeric.c
index 90db8aab96..801370aa43 100644
--- a/numeric.c
+++ b/numeric.c
@@ -4147,6 +4147,8 @@ rb_num_pow(VALUE x, VALUE y)
         return rb_complex_pow(x, y);
       case T_RATIONAL:
         return rb_rational_pow(x, y);
+      default:
+        break;
     }
     return Qnil;
 }
diff --git a/object.c b/object.c
index ea2b47c769..dfe3d14e6e 100644
--- a/object.c
+++ b/object.c
@@ -3917,6 +3917,8 @@ rb_num_to_dbl(VALUE val)
 	    if (basic_to_f_p(rb_cRational))
 		return rat2dbl_without_to_f(val);
 	    break;
+          default:
+	    break;
 	}
     }
     val = numeric_to_float(val);
@@ -3954,6 +3956,8 @@ rb_num2dbl(VALUE val)
 	    return rat2dbl_without_to_f(val);
 	  case T_STRING:
 	    rb_raise(rb_eTypeError, "no implicit conversion to float from string");
+          default:
+	    break;
 	}
     }
     val = rb_convert_type_with_id(val, T_FLOAT, "Float", id_to_f);
@@ -4132,6 +4136,8 @@ rb_obj_dig(int argc, VALUE *argv, VALUE obj, VALUE notfound)
 		    continue;
 		}
 		break;
+              default:
+                break;
 	    }
 	}
         return rb_check_funcall_with_hook_kw(obj, id_dig, argc, argv,
diff --git a/proc.c b/proc.c
index 9164c27ff8..50ebdbde67 100644
--- a/proc.c
+++ b/proc.c
@@ -1827,6 +1827,9 @@ rb_method_name_error(VALUE klass, VALUE str)
 	  case T_CLASS:
 	    c = obj;
 	    s = MSG("");
+            break;
+          default:
+	    break;
 	}
 	goto normal_class;
     }
diff --git a/process.c b/process.c
index b45c79cca3..3d3fef12ff 100644
--- a/process.c
+++ b/process.c
@@ -2390,6 +2390,8 @@ check_hash(VALUE obj)
       case T_STRING:
       case T_ARRAY:
 	return Qnil;
+      default:
+        break;
     }
     return rb_check_hash_type(obj);
 }
diff --git a/range.c b/range.c
index a77d324f85..2444f0588d 100644
--- a/range.c
+++ b/range.c
@@ -318,6 +318,8 @@ linear_object_p(VALUE obj)
       case T_FLOAT:
       case T_BIGNUM:
 	return TRUE;
+      default:
+        break;
     }
     if (rb_obj_is_kind_of(obj, rb_cNumeric)) return TRUE;
     if (rb_obj_is_kind_of(obj, rb_cTime)) return TRUE;
diff --git a/variable.c b/variable.c
index 94bac4a272..9ff0326a14 100644
--- a/variable.c
+++ b/variable.c
@@ -72,6 +72,7 @@ rb_namespace_p(VALUE obj)
     if (RB_SPECIAL_CONST_P(obj)) return false;
     switch (RB_BUILTIN_TYPE(obj)) {
       case T_MODULE: case T_CLASS: return true;
+      default: break;
     }
     return false;
 }
diff --git a/vm_method.c b/vm_method.c
index de58f7d0a7..afda598aa1 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -524,6 +524,8 @@ filter_defined_class(VALUE klass)
 	return 0;
       case T_ICLASS:
 	break;
+      default:
+        break;
     }
     rb_bug("filter_defined_class: %s", rb_obj_info(klass));
 }