diff --git a/lib/net/http/header.rb b/lib/net/http/header.rb
index b0ec4b06..ef95e6c6 100644
--- a/lib/net/http/header.rb
+++ b/lib/net/http/header.rb
@@ -20,10 +20,12 @@ def initialize_http_header(initheader)
       else
         value = value.strip # raise error for invalid byte sequences
         if value.count("\r\n") > 0
-          raise ArgumentError, "header #{key} has field value #{value.inspect}, this cannot include CR/LF"
+          raise Net::HTTPHeaderSyntaxError, "header #{key} has field value #{value.inspect}, this cannot include CR/LF"
         end
         @header[key.downcase.to_s] = [value]
       end
+    rescue ArgumentError => e
+      raise Net::HTTPHeaderSyntaxError, e.message
     end
   end
 
@@ -82,7 +84,7 @@ def add_field(key, val)
     else
       val = val.to_s # for compatibility use to_s instead of to_str
       if val.b.count("\r\n") > 0
-        raise ArgumentError, 'header field value cannot include CR/LF'
+        raise Net::HTTPHeaderSyntaxError, 'header field value cannot include CR/LF'
       end
       @header[key.downcase.to_s] = [val]
     end
@@ -95,7 +97,7 @@ def add_field(key, val)
     else
       val = val.to_s
       if /[\r\n]/n.match?(val.b)
-        raise ArgumentError, 'header field value cannot include CR/LF'
+        raise Net::HTTPHeaderSyntaxError, 'header field value cannot include CR/LF'
       end
       ary.push val
     end
@@ -481,7 +483,7 @@ def set_form(params, enctype='application/x-www-form-urlencoded', formopt={})
       /\Amultipart\/form-data\z/i
       self.content_type = enctype
     else
-      raise ArgumentError, "invalid enctype: #{enctype}"
+      raise Net::HTTPHeaderSyntaxError, "invalid enctype: #{enctype}"
     end
   end
 
diff --git a/test/net/http/test_httpheader.rb b/test/net/http/test_httpheader.rb
index b1ca9e82..4505877a 100644
--- a/test/net/http/test_httpheader.rb
+++ b/test/net/http/test_httpheader.rb
@@ -26,9 +26,9 @@ def test_initialize
     @c.initialize_http_header([["foo", "abc"], ["bar","xyz"]])
     assert_equal "xyz", @c["bar"]
     assert_raise(NoMethodError){ @c.initialize_http_header("foo"=>[]) }
-    assert_raise(ArgumentError){ @c.initialize_http_header("foo"=>"a\nb") }
-    assert_raise(ArgumentError){ @c.initialize_http_header("foo"=>"a\rb") }
-    assert_raise(ArgumentError){ @c.initialize_http_header("foo"=>"a\xff") }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c.initialize_http_header("foo"=>"a\nb") }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c.initialize_http_header("foo"=>"a\rb") }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c.initialize_http_header("foo"=>"a\xff") }
   end
 
   def test_initialize_with_symbol
@@ -68,8 +68,8 @@ def test_ASET
     @c['aaa'] = "aaa\xff"
     assert_equal 2, @c.length
 
-    assert_raise(ArgumentError){ @c['foo'] = "a\nb" }
-    assert_raise(ArgumentError){ @c['foo'] = ["a\nb"] }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c['foo'] = "a\nb" }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c['foo'] = ["a\nb"] }
   end
 
   def test_AREF
@@ -95,7 +95,7 @@ def test_add_field
     @c.add_field 'My-Header', 'd, d'
     assert_equal 'a, b, c, d, d', @c['My-Header']
     assert_equal ['a', 'b', 'c', 'd, d'], @c.get_fields('My-Header')
-    assert_raise(ArgumentError){ @c.add_field 'My-Header', "d\nd" }
+    assert_raise(Net::HTTPHeaderSyntaxError){ @c.add_field 'My-Header', "d\nd" }
     @c.add_field 'My-Header', ['e', ["\xff", 7]]
     assert_equal "a, b, c, d, d, e, \xff, 7", @c['My-Header']
     assert_equal ['a', 'b', 'c', 'd, d', 'e', "\xff", '7'], @c.get_fields('My-Header')