diff --git a/build/arduino-builder-linux32-1.0.0-beta20.tar.bz2.sha b/build/arduino-builder-linux32-1.0.0-beta20.tar.bz2.sha
deleted file mode 100644
index bc15420c6..000000000
--- a/build/arduino-builder-linux32-1.0.0-beta20.tar.bz2.sha
+++ /dev/null
@@ -1 +0,0 @@
-8ac7004e89d12cd891e8cf92c3c5f86cac7e3bb8
diff --git a/build/arduino-builder-linux32-1.0.0-beta21.tar.bz2.sha b/build/arduino-builder-linux32-1.0.0-beta21.tar.bz2.sha
new file mode 100644
index 000000000..70180fb1f
--- /dev/null
+++ b/build/arduino-builder-linux32-1.0.0-beta21.tar.bz2.sha
@@ -0,0 +1 @@
+c6366e28b4dd94acc1d223f23b7e22c087195ff6
diff --git a/build/arduino-builder-linux64-1.0.0-beta20.tar.bz2.sha b/build/arduino-builder-linux64-1.0.0-beta20.tar.bz2.sha
deleted file mode 100644
index b00defc93..000000000
--- a/build/arduino-builder-linux64-1.0.0-beta20.tar.bz2.sha
+++ /dev/null
@@ -1 +0,0 @@
-50a40200f3a68f1f1b6cfbf7ed3266c575e3d9f3
diff --git a/build/arduino-builder-linux64-1.0.0-beta21.tar.bz2.sha b/build/arduino-builder-linux64-1.0.0-beta21.tar.bz2.sha
new file mode 100644
index 000000000..1323925a9
--- /dev/null
+++ b/build/arduino-builder-linux64-1.0.0-beta21.tar.bz2.sha
@@ -0,0 +1 @@
+6d0f1a93c9c98a8a579447c22086ef3b773adc9e
diff --git a/build/arduino-builder-macosx-1.0.0-beta20.tar.bz2.sha b/build/arduino-builder-macosx-1.0.0-beta20.tar.bz2.sha
deleted file mode 100644
index d6e5e5727..000000000
--- a/build/arduino-builder-macosx-1.0.0-beta20.tar.bz2.sha
+++ /dev/null
@@ -1 +0,0 @@
-cb4c4e8c20487a2164cbb66b2b987c1ffdb1fdfd
diff --git a/build/arduino-builder-macosx-1.0.0-beta21.tar.bz2.sha b/build/arduino-builder-macosx-1.0.0-beta21.tar.bz2.sha
new file mode 100644
index 000000000..f56e4624e
--- /dev/null
+++ b/build/arduino-builder-macosx-1.0.0-beta21.tar.bz2.sha
@@ -0,0 +1 @@
+50c50ccbfd1dc8ee896b4d13b5391a54b94a4606
diff --git a/build/arduino-builder-windows-1.0.0-beta20.zip.sha b/build/arduino-builder-windows-1.0.0-beta20.zip.sha
deleted file mode 100644
index 46d067bc5..000000000
--- a/build/arduino-builder-windows-1.0.0-beta20.zip.sha
+++ /dev/null
@@ -1 +0,0 @@
-68ae5d705966bc53d994aa50bf87ea1db1243390
diff --git a/build/arduino-builder-windows-1.0.0-beta21.zip.sha b/build/arduino-builder-windows-1.0.0-beta21.zip.sha
new file mode 100644
index 000000000..b5537f650
--- /dev/null
+++ b/build/arduino-builder-windows-1.0.0-beta21.zip.sha
@@ -0,0 +1 @@
+2d03546347d26b2130af35d1dac0a097c9f35753
diff --git a/build/build.xml b/build/build.xml
index 4b59408f8..96237414e 100644
--- a/build/build.xml
+++ b/build/build.xml
@@ -71,7 +71,7 @@
     </or>
   </condition>
 
-  <property name="ARDUINO-BUILDER-VERSION" value="1.0.0-beta20" />
+  <property name="ARDUINO-BUILDER-VERSION" value="1.0.0-beta21" />
 
   <!-- Libraries required for running arduino -->
   <fileset dir=".." id="runtime.jars">
diff --git a/build/shared/revisions.txt b/build/shared/revisions.txt
index 98684f8ae..e94b71d47 100644
--- a/build/shared/revisions.txt
+++ b/build/shared/revisions.txt
@@ -22,6 +22,7 @@ ARDUINO 1.6.6
 * Each open sketch gets built in its own folder, allowing the IDE to recycle previous compilations and being much faster
 * "Go to line": CTRL+L or Edit > Go to line... will open a dialog where you can type the line number where you want the editor to jump to
 * Added boards.local.txt support: like platform.local.txt, allows to enrich a boards.txt definition without modifying the original file. Thanks @Wackerbarth
+* Library to library dependencies: when your sketch imports a library, and that library uses another, the IDE will find out without you having to add a useless #include to your sketch
 
 [libraries]
 * Bridge: YunClient.connected() returns true if there are bytes available for read. Thanks @RobAtticus