diff --git a/ARM.CMSIS.pdsc b/ARM.CMSIS.pdsc
index b3ca667..9d86218 100644
--- a/ARM.CMSIS.pdsc
+++ b/ARM.CMSIS.pdsc
@@ -8,6 +8,9 @@
   <url>http://www.keil.com/pack/</url>
 
   <releases>
+    <release version="5.5.1-dev0">
+      Active development...
+    </release>
     <release version="5.5.0-rc1" date="2019-03-15">
       The following folders have been removed:
         - CMSIS/Include/ (superseded by CMSIS/DSP/Include/ and CMSIS/Core/Include/)