diff --git a/Changes b/Changes
index 0da993f..2e6ea97 100644
--- a/Changes
+++ b/Changes
@@ -1,4 +1,4 @@
-0.25 2017-02-20
+0.25 2017-03-14
         - Updated to Mojolicious 7.20
         - Fixed meta treatment in case analytic and monogr
           are available
@@ -9,6 +9,7 @@
         - Renamed "pages" to "srcPages".
         - Fixed handling of prefixes for text sigles.
         - Support for MarMoT.
+        - Fix case insensitivity.
 
 0.24 2016-12-21
         - Added --base-sentences and --base-paragraphs options
diff --git a/Makefile.PL b/Makefile.PL
index 56ab8ee..966bda5 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -28,6 +28,7 @@
     'File::Temp'      => 0,
     'Directory::Iterator' => 0,
     'Benchmark'       => 0,
+    'Unicode::CaseFold' => 1.00,
     'Carp'            => 0,
     'strict'          => 0,
     'warnings'        => 0,
diff --git a/lib/KorAP/XML/Tokenizer.pm b/lib/KorAP/XML/Tokenizer.pm
index b89f92c..4889417 100644
--- a/lib/KorAP/XML/Tokenizer.pm
+++ b/lib/KorAP/XML/Tokenizer.pm
@@ -11,6 +11,7 @@
 use KorAP::XML::Tokenizer::Spans;
 use KorAP::XML::Tokenizer::Tokens;
 use KorAP::XML::Index::MultiTermTokenStream;
+use Unicode::CaseFold;
 use List::MoreUtils 'uniq';
 use JSON::XS;
 use Log::Log4perl;
@@ -156,7 +157,7 @@
     $mtt->add('s:' . $token);
 
     # Add case insensitive term
-    $mtt->add('i:' . lc $token);
+    $mtt->add('i:' . fc $token);
 
     # Add offset information
     $mtt->o_start($from);