diff --git a/lib/ipaddr.rb b/lib/ipaddr.rb
index 898af26..1d6d595 100644
--- a/lib/ipaddr.rb
+++ b/lib/ipaddr.rb
@@ -617,7 +617,7 @@ def zone_id
   def zone_id=(zid)
     if @family == Socket::AF_INET6
       case zid
-      when nil, /\A%(\w+)\z/
+      when nil, /\A%[-0-9A-Za-z._~]+\z/
         @zone_id = zid
       else
         raise InvalidAddressError, "invalid zone identifier for address"
@@ -758,7 +758,7 @@ def initialize(addr = '::', family = Socket::AF_UNSPEC)
       family = Socket::AF_INET6
       bracketed = true
     end
-    if prefix =~ /\A(.*)(%\w+)\z/
+    if prefix =~ /\A(.*)(%[-0-9A-Za-z._~]+)\z/
       prefix = $1
       zone_id = $2
       family = Socket::AF_INET6
diff --git a/test/test_ipaddr.rb b/test/test_ipaddr.rb
index daa68e6..5727239 100644
--- a/test/test_ipaddr.rb
+++ b/test/test_ipaddr.rb
@@ -302,6 +302,9 @@ def test_to_s_with_zone_id
     assert_equal("::192.168.1.2%eth0", IPAddr.new("::192.168.1.2%eth0").to_s)
     assert_equal("fe80::1%0ab", IPAddr.new("fe80::1%0ab").to_s)
     assert_equal("fe80::1%0012", IPAddr.new("fe80::1%0012").to_s)
+    assert_equal("fe80::1%eth0.100", IPAddr.new("fe80::1%eth0.100").to_s)
+    assert_equal("fe80::1%br-lan", IPAddr.new("fe80::1%br-lan").to_s)
+    assert_equal("fe80::%a~b/64", IPAddr.new("fe80::1%a~b/64").cidr)
   end
 
   def test_to_bits
@@ -389,6 +392,12 @@ def test_zone_id
     assert_equal('%ab0', a.zone_id)
     assert_equal("1:2:3:4:5:6:7:8%ab0", a.to_s)
     assert_raise(IPAddr::InvalidAddressError) { a.zone_id = '%' }
+    a.zone_id = '%eth0.100'
+    assert_equal("1:2:3:4:5:6:7:8%eth0.100", a.to_s)
+    a.zone_id = '%br-lan'
+    assert_equal('%br-lan', a.zone_id)
+    assert_raise(IPAddr::InvalidAddressError) { a.zone_id = '%a b' }
+    assert_raise(IPAddr::InvalidAddressError) { a.zone_id = '%a/b' }
   end
 
   def test_to_range