diff --git a/lib/linguist/mime.rb b/lib/linguist/mime.rb
index e8203169..e4303ddb 100644
--- a/lib/linguist/mime.rb
+++ b/lib/linguist/mime.rb
@@ -9,8 +9,6 @@ module MIME
     def binary?
       if defined? @binary
         @binary
-      elsif media_type == 'text'
-        false
       else
         @encoding == 'base64'
       end
@@ -25,7 +23,17 @@ mime_extensions.each do |mime_type, options|
 
   (options['extensions'] || []).each { |ext| mime.extensions << ext }
 
-  mime.binary = options['binary']     if options.key?('binary')
+  (options['exclude_extensions'] || []).each do |ext|
+    mime.extensions.delete(ext)
+
+    MIME::Types.instance_eval do
+      @__types__.instance_eval do
+        @extension_index[ext].delete(mime)
+      end
+    end
+  end
+
+  mime.binary = options['binary'] if options.key?('binary')
 
   MIME::Types.add_type_variant(mime)
   MIME::Types.index_extensions(mime)
diff --git a/lib/linguist/mimes.yml b/lib/linguist/mimes.yml
index 20bc180c..c3ee7000 100644
--- a/lib/linguist/mimes.yml
+++ b/lib/linguist/mimes.yml
@@ -21,6 +21,10 @@ application/x-troff-ms:
 application/netcdf:
   binary: false
 
+application/x-pagemaker:
+  exclude_extensions:
+  - pm
+
 application/x-perl:
   binary: false
 
diff --git a/test/test_mime.rb b/test/test_mime.rb
index 21859c65..7c0e49ec 100644
--- a/test/test_mime.rb
+++ b/test/test_mime.rb
@@ -9,9 +9,11 @@ class TestMime < Test::Unit::TestCase
     assert_equal 'text/plain', Mime.mime_for(nil)
     assert_equal 'text/plain', Mime.mime_for("")
 
-    assert_equal 'application/ruby', Mime.mime_for(".rb")
     assert_equal 'application/javascript', Mime.mime_for(".js")
+    assert_equal 'application/perl', Mime.mime_for(".pl")
+    assert_equal 'application/perl', Mime.mime_for(".pm")
     assert_equal 'application/python', Mime.mime_for(".py")
+    assert_equal 'application/ruby', Mime.mime_for(".rb")
 
     assert_equal 'text/plain', Mime.mime_for(".kt")
     assert_equal 'text/html', Mime.mime_for(".html")
@@ -108,6 +110,7 @@ class TestMime < Test::Unit::TestCase
     assert !Mime.binary?("application/atom+xml")
     assert !Mime.binary?("application/javascript")
     assert !Mime.binary?("application/json")
+    assert !Mime.binary?("application/perl")
     assert !Mime.binary?("application/rdf+xml")
     assert !Mime.binary?("application/sh")
     assert !Mime.binary?("application/x-ms-xbap")
@@ -128,6 +131,7 @@ class TestMime < Test::Unit::TestCase
     assert !Mime.binary?(".ms")
     assert !Mime.binary?(".nc")
     assert !Mime.binary?(".pl")
+    assert !Mime.binary?(".pm")
     assert !Mime.binary?(".py")
     assert !Mime.binary?(".rb")
     assert !Mime.binary?(".sh")