diff --git a/lib/yard/cli/yardoc.rb b/lib/yard/cli/yardoc.rb
index f40e4dd15..18a955086 100644
--- a/lib/yard/cli/yardoc.rb
+++ b/lib/yard/cli/yardoc.rb
@@ -411,14 +411,27 @@ def print_list
       def add_extra_files(*files)
         files.map! {|f| f.include?("*") ? Dir.glob(f) : f }.flatten!
         files.each do |file|
-          if File.file?(file)
+          if extra_file_valid?(file)
             options.files << CodeObjects::ExtraFileObject.new(file)
-          else
-            log.warn "Could not find extra file: #{file}"
           end
         end
       end
 
+      # @param file [String] the filename to validate
+      # @param check_exists [Boolean] whether the file should exist on disk
+      # @return [Boolean] whether the file is allowed to be used
+      def extra_file_valid?(file, check_exists = true)
+        if file =~ %r{^(?:\.\./|/)}
+          log.warn "Invalid file: #{file}"
+          false
+        elsif check_exists && !File.file?(file)
+          log.warn "Could not find file: #{file}"
+          false
+        else
+          true
+        end
+      end
+
       # Parses the file arguments into Ruby files and extra files, which are
       # separated by a '-' element.
       #
@@ -644,10 +657,8 @@ def output_options(opts)
 
         opts.on('-r', '--readme FILE', '--main FILE', 'The readme file used as the title page',
                                                       '  of documentation.') do |readme|
-          if File.file?(readme)
+          if extra_file_valid?(readme)
             options.readme = CodeObjects::ExtraFileObject.new(readme)
-          else
-            log.warn "Could not find readme file: #{readme}"
           end
         end
 
@@ -658,12 +669,9 @@ def output_options(opts)
 
         opts.on('--asset FROM[:TO]', 'A file or directory to copy over to output ',
                                      '  directory after generating') do |asset|
-          re = %r{^(?:\.\./|/)}
           from, to = *asset.split(':').map {|f| File.cleanpath(f, true) }
           to ||= from
-          if from =~ re || to =~ re
-            log.warn "Invalid file '#{asset}'"
-          else
+          if extra_file_valid?(from, false) && extra_file_valid?(to, false)
             assets[from] = to
           end
         end
diff --git a/spec/cli/yardoc_spec.rb b/spec/cli/yardoc_spec.rb
index 2525ec52c..5b39bd263 100644
--- a/spec/cli/yardoc_spec.rb
+++ b/spec/cli/yardoc_spec.rb
@@ -205,10 +205,10 @@ def self.should_accept(*args, &block)
     end
 
     it "aliases --main to the --readme flag" do
-      readme = File.join(File.dirname(__FILE__), '..', '..', 'README.md')
-
-      @yardoc.parse_arguments('--main', readme)
-      expect(@yardoc.options.readme).to eq CodeObjects::ExtraFileObject.new(readme, '')
+      Dir.chdir(File.join(File.dirname(__FILE__), '..', '..')) do
+        @yardoc.parse_arguments('--main', 'README.md')
+        expect(@yardoc.options.readme).to eq CodeObjects::ExtraFileObject.new('README.md', '')
+      end
     end
 
     it "selects a markup provider when --markup-provider or -mp is set" do
@@ -607,15 +607,25 @@ def foo; end
     end
 
     it "warns if extra file is not found" do
-      expect(log).to receive(:warn).with(/Could not find extra file: UNKNOWN/)
+      expect(log).to receive(:warn).with(/Could not find file: UNKNOWN/)
       @yardoc.parse_arguments(*%w(- UNKNOWN))
     end
 
     it "warns if readme file is not found" do
-      expect(log).to receive(:warn).with(/Could not find readme file: UNKNOWN/)
+      expect(log).to receive(:warn).with(/Could not find file: UNKNOWN/)
       @yardoc.parse_arguments(*%w(-r UNKNOWN))
     end
 
+    it "warns on absolute paths in extra files" do
+      expect(log).to receive(:warn).with(%r{Invalid file: /path/to/file})
+      @yardoc.parse_arguments(*%w(- /path/to/file))
+    end
+
+    it "warns on absolute paths in readme" do
+      expect(log).to receive(:warn).with(%r{Invalid file: /path/to/file})
+      @yardoc.parse_arguments(*%w(-r /path/to/file))
+    end
+
     it "uses first file as readme if no readme is specified when using --one-file" do
       expect(Dir).to receive(:glob).with('README{,*[^~]}').and_return []
       expect(Dir).to receive(:glob).with('lib/*.rb').and_return(['lib/foo.rb'])