diff --git a/lib/rdf/model/uri.rb b/lib/rdf/model/uri.rb
index f56391eb..878ffd1d 100644
--- a/lib/rdf/model/uri.rb
+++ b/lib/rdf/model/uri.rb
@@ -70,10 +70,10 @@ class URI
     IUSERINFO = Regexp.compile("(?:(?:#{IUNRESERVED})|(?:#{PCT_ENCODED})|(?:#{SUB_DELIMS})|:)*").freeze
     IAUTHORITY = Regexp.compile("(?:#{IUSERINFO}@)?#{IHOST}(?::#{PORT})?").freeze
     
-    IRELATIVE_PART = Regexp.compile("(?:(?://#{IAUTHORITY}(?:#{IPATH_ABEMPTY}))|(?:#{IPATH_ABSOLUTE})|(?:#{IPATH_NOSCHEME})|(?:#{IPATH_EMPTY}))").freeze
-    IRELATIVE_REF = Regexp.compile("^#{IRELATIVE_PART}(?:\\?#{IQUERY})?(?:\\##{IFRAGMENT})?$").freeze
+    IRELATIVE_PART = Regexp.compile("//#{IAUTHORITY}(?:#{IPATH_ABEMPTY})|(?:#{IPATH_ABSOLUTE})|(?:#{IPATH_NOSCHEME})|(?:#{IPATH_EMPTY})").freeze
+    IRELATIVE_REF = Regexp.compile("^(?:#{IRELATIVE_PART})(?:\\?#{IQUERY})?(?:\\##{IFRAGMENT})?$").freeze
 
-    IHIER_PART = Regexp.compile("(?:(?://#{IAUTHORITY}#{IPATH_ABEMPTY})|(?:#{IPATH_ABSOLUTE})|(?:#{IPATH_ROOTLESS})|(?:#{IPATH_EMPTY}))").freeze
+    IHIER_PART = Regexp.compile("//#{IAUTHORITY}(?:#{IPATH_ABEMPTY})|(?:#{IPATH_ABSOLUTE})|(?:#{IPATH_ROOTLESS})|(?:#{IPATH_EMPTY})").freeze
     IRI = Regexp.compile("^#{SCHEME}:(?:#{IHIER_PART})(?:\\?#{IQUERY})?(?:\\##{IFRAGMENT})?$").freeze
 
     # Split an IRI into it's component parts