diff --git a/lib/linguist/heuristics.rb b/lib/linguist/heuristics.rb
index 876e974dc9..fe680382e5 100644
--- a/lib/linguist/heuristics.rb
+++ b/lib/linguist/heuristics.rb
@@ -45,20 +45,29 @@ def self.load()
         exts = disambiguation['extensions']
         rules = disambiguation['rules']
         rules.map! do |rule|
-          if !rule['pattern'].nil?
-            rule['pattern'] = self.to_regex(rule['pattern'])
-          elsif !rule['negative_pattern'].nil?
-            pat = self.to_regex(rule['negative_pattern'])
-            rule['pattern'] = NegativePattern.new(pat)
-          elsif !rule['named_pattern'].nil?
-            rule['pattern'] = named_patterns[rule['named_pattern']]
-          end
+          rule['pattern'] = self.parse_rule(named_patterns, rule)
           rule
         end
         @heuristics << new(exts, rules)
       end
     end
 
+    def self.parse_rule(named_patterns, rule)
+      if !rule['and'].nil?
+        rules = rule['and'].map { |block| self.parse_rule(named_patterns, block) }
+        return And.new(rules)
+      elsif !rule['pattern'].nil?
+        return self.to_regex(rule['pattern'])
+      elsif !rule['negative_pattern'].nil?
+        pat = self.to_regex(rule['negative_pattern'])
+        return NegativePattern.new(pat)
+      elsif !rule['named_pattern'].nil?
+        return named_patterns[rule['named_pattern']]
+      else
+        return AlwaysMatch.new()
+      end
+    end
+
     # Internal: Converts a string or array of strings to regexp
     #
     # str: string or array of strings. If it is an array of strings,
@@ -91,8 +100,7 @@ def matches?(filename, candidates)
     # Internal: Perform the heuristic
     def call(data)
       matched = @rules.find do |rule|
-        m = !rule.key?('pattern') || rule['pattern'].match(data)
-        m
+        rule['pattern'].match(data)
       end
       if !matched.nil?
         languages = matched['language']
@@ -106,6 +114,24 @@ def call(data)
 
   end
 
+  class And
+
+    def initialize(pats)
+      @pats = pats
+    end
+
+    def match(input)
+      return !@pats.any? { |pat| !pat.match(input) }
+    end
+
+  end
+
+  class AlwaysMatch
+    def match(input)
+      return true
+    end
+  end
+
   class NegativePattern
 
     def initialize(pat)
diff --git a/lib/linguist/heuristics.yml b/lib/linguist/heuristics.yml
index 24b409f962..79736ab392 100644
--- a/lib/linguist/heuristics.yml
+++ b/lib/linguist/heuristics.yml
@@ -16,6 +16,8 @@
 #                       Pattern can be a string with a single regular expression
 #                       or an array of strings that will be merged in a single
 #                       regular expression (with union).
+# and                 - An and block merges multiple rules and checks that all of
+#                       of them must match.
 # negative_pattern    - Same as pattern, but checks for absence of matches.
 # named_pattern       - A pattern can be reused by specifying it in the
 #                       named_patterns section and referencing it here by its
@@ -217,9 +219,9 @@ disambiguations:
   - language: Roff
     pattern: '^[.''][A-Za-z]{2}(\s|$)'
   - language: Unix Assembly
-    pattern:
-    - '(?<!\S)\.(include|globa?l)\s|(?<!\/\*)(\A|\n)\s*\.[A-Za-z][_A-Za-z0-9]*:'
-    #TODO: !/\/\*/.match(data) && /^\s*\.(?:include\s|globa?l\s|[A-Za-z][_A-Za-z0-9]*:)/.match(data)
+    and:
+      - negative_pattern: '/\*'
+      - pattern: '^\s*\.(?:include\s|globa?l\s|[A-Za-z][_A-Za-z0-9]*:)'
   - language: MAXScript
 - extensions: ['.n']
   rules:
@@ -267,7 +269,9 @@ disambiguations:
   - language: INI
     pattern: 'last_client='
   - language: QMake
-    pattern: '(HEADERS|SOURCES)'
+    and:
+    - pattern: HEADERS
+    - pattern: SOURCES
   - language: IDL
     pattern: '^\s*function[ \w,]+$'
 - extensions: ['.props']