diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 2999f75c7f..e0296914fc 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Inflections: MatrixTest -> MatrixTests instead of MatricesTest.  #8496 [jbwiv]
+
 * Multibyte strings respond_to the String methods they proxy so they can be duck-typed.  #6549 [Tuxie]
 
 * Array#to_xml yields the builder just like Hash and ActiveRecord::Base.  #8472 [seth]
diff --git a/activesupport/lib/active_support/inflections.rb b/activesupport/lib/active_support/inflections.rb
index 8f3f8618cc..f53ef53ca4 100644
--- a/activesupport/lib/active_support/inflections.rb
+++ b/activesupport/lib/active_support/inflections.rb
@@ -12,7 +12,7 @@ Inflector.inflections do |inflect|
   inflect.plural(/(hive)$/i, '\1s')
   inflect.plural(/([^aeiouy]|qu)y$/i, '\1ies')
   inflect.plural(/(x|ch|ss|sh)$/i, '\1es')
-  inflect.plural(/(matr|vert|ind)ix|ex$/i, '\1ices')
+  inflect.plural(/(matr|vert|ind)(?:ix|ex)$/i, '\1ices')
   inflect.plural(/([m|l])ouse$/i, '\1ice')
   inflect.plural(/^(ox)$/i, '\1en')
   inflect.plural(/(quiz)$/i, '\1zes')
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index 3aff541646..9849e0b52b 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -45,6 +45,7 @@ class InflectorTest < Test::Unit::TestCase
 
     "basis"       => "bases",
     "diagnosis"   => "diagnoses",
+    "diagnosis_a" => "diagnosis_as",
 
     "datum"       => "data",
     "medium"      => "media",
@@ -92,6 +93,7 @@ class InflectorTest < Test::Unit::TestCase
 
     "vertex"      => "vertices",
     "matrix"      => "matrices",
+    "matrix_fu"   => "matrix_fus",
 
     "axis"        => "axes",
     "testis"      => "testes",