diff --git a/lib/linguist/heuristics.rb b/lib/linguist/heuristics.rb
index 200e83f2..8ef2f41c 100644
--- a/lib/linguist/heuristics.rb
+++ b/lib/linguist/heuristics.rb
@@ -22,6 +22,9 @@ module Linguist
         if languages.all? { |l| ["TypeScript", "XML"].include?(l) }
           disambiguate_ts(data, languages)
         end
+        if languages.all? { |l| ["Common Lisp", "OpenCL"].include?(l) }
+          disambiguate_cl(data, languages)
+        end
       end
     end
 
@@ -53,6 +56,13 @@ module Linguist
       matches
     end
 
+    def self.disambiguate_cl(data, languages)
+      matches = []
+      matches << Language["Common Lisp"] if data.include?("(defun ")
+      matches << Language["OpenCL"] if /\/\* |\/\/ |^\}/.match(data)
+      matches
+    end
+
     def self.active?
       !!ACTIVE
     end
diff --git a/test/test_heuristics.rb b/test/test_heuristics.rb
index 148f49c5..3d063dd3 100644
--- a/test/test_heuristics.rb
+++ b/test/test_heuristics.rb
@@ -15,14 +15,14 @@ class TestHeuristcs < Test::Unit::TestCase
     File.read(File.join(samples_path, name))
   end
 
-  # Only calling out '.h' filenames as these are the ones causing issues
-  def all_h_fixtures(language_name)
-    Dir.glob("#{samples_path}/#{language_name}/*.h")
+  def all_fixtures(language_name, file="*")
+    Dir.glob("#{samples_path}/#{language_name}/#{file}")
   end
 
   def test_obj_c_by_heuristics
     languages = ["C++", "Objective-C"]
-    all_h_fixtures("Objective-C").each do |fixture|
+    # Only calling out '.h' filenames as these are the ones causing issues
+    all_fixtures("Objective-C", "*.h").each do |fixture|
       results = Heuristics.disambiguate_c(fixture("Objective-C/#{File.basename(fixture)}"), languages)
       assert_equal Language["Objective-C"], results.first
     end
@@ -62,4 +62,14 @@ class TestHeuristcs < Test::Unit::TestCase
     results = Heuristics.disambiguate_ts(fixture("XML/pt_BR.xml"), languages)
     assert_equal Language["XML"], results.first
   end
+
+  def test_cl_by_heuristics
+    languages = ["Common Lisp", "OpenCL"]
+    languages.each do |language|
+      all_fixtures(language).each do |fixture|
+        results = Heuristics.disambiguate_cl(fixture("#{language}/#{File.basename(fixture)}"), languages)
+        assert_equal Language[language], results.first
+      end
+    end
+  end
 end