diff --git a/lib/rouge/lexers/ruby.rb b/lib/rouge/lexers/ruby.rb
index 5f07cc3728..e76a4742d1 100644
--- a/lib/rouge/lexers/ruby.rb
+++ b/lib/rouge/lexers/ruby.rb
@@ -183,7 +183,7 @@ def self.detect?(text)
 
         mixin :strings
 
-        rule %r/(?:#{keywords.join('|')})\b/, Keyword, :expr_start
+        rule %r/(?:#{keywords.join('|')})(?=\W|$)/, Keyword, :expr_start
         rule %r/(?:#{keywords_pseudo.join('|')})\b/, Keyword::Pseudo, :expr_start
 
         rule %r(
diff --git a/spec/visual/samples/ruby b/spec/visual/samples/ruby
index ad4604aef9..2e6b59befd 100644
--- a/spec/visual/samples/ruby
+++ b/spec/visual/samples/ruby
@@ -49,6 +49,35 @@ a/ b #comment
 x.a / 1 # comment
 Foo::a / 3 + 4
 
+########
+# Keywords that may be immediately followed by an opening
+# parenthesis
+########
+
+# defined?
+return if defined? Rouge
+return unless defined?(Foobar)
+
+# super
+class Beta < Alpha
+  def gamma(msg)
+    super
+    @msg = msg
+  end
+end
+
+class Bar < Foo
+  def log(msg)
+    super()
+  end
+end
+
+class Ipsum < Lorem
+  def dolor(txt)
+    super(txt)
+  end
+end
+
 ########
 # The popular . :bow:
 ########