diff --git a/lib/linguist/heuristics.rb b/lib/linguist/heuristics.rb
index 88e973fc..1b2c2a5b 100644
--- a/lib/linguist/heuristics.rb
+++ b/lib/linguist/heuristics.rb
@@ -295,7 +295,7 @@ module Linguist
         Language["Common Lisp"]
       elsif /^(%[%{}]xs|<.*>)/.match(data)
         Language["Lex"]
-      elsif /^\.[a-z][a-z](\s|$)/.match(data)
+      elsif /^\.[a-z][a-z](\s|$)/i.match(data)
         Language["Groff"]
       end
     end
@@ -307,5 +307,13 @@ module Linguist
         Language["Nemerle"]
       end
     end
+
+    disambiguate "GAS", "Groff" do |data|
+      if /^[.'][a-z][a-z](\s|$)/i.match(data)
+        Language["Groff"]
+      elsif /((^|\s)move?[. ])|\.(include|globa?l)\s/.match(data)
+        Language["GAS"]
+      end
+    end
   end
 end
diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 4beaa7aa..c1598bff 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -1041,6 +1041,7 @@ GAS:
   group: Assembly
   extensions:
   - .s
+  - .ms
   tm_scope: source.asm.x86
   ace_mode: assembly_x86