diff --git a/build/shared/revisions.txt b/build/shared/revisions.txt
index 6566c2526..e87448663 100644
--- a/build/shared/revisions.txt
+++ b/build/shared/revisions.txt
@@ -9,6 +9,9 @@ The following changes are included also in the Arduino IDE 1.0.7:
 [libraries]
 * EthernetClien: use IANA recommended ephemeral port range, 49152-65535 (Jack Christensen, cifer-lee)
 
+[core]
+* Fixed regression in HardwareSerial::available() introduced with https://github.com/arduino/Arduino/pull/2057
+
 ARDUINO 1.5.8 BETA - 2014.10.01
 
 [ide]
@@ -346,6 +349,10 @@ ARDUINO 1.0.7
 * Backported GSM from IDE 1.5.x
 * EthernetClien: use IANA recommended ephemeral port range, 49152-65535 (Jack Christensen, cifer-lee)
 
+[core]
+* Fixed missing NOT_AN_INTERRUPT constant in digitalPinToInterrupt() macro
+* Fixed regression in HardwareSerial::available() introduced with https://github.com/arduino/Arduino/pull/2057
+
 ARDUINO 1.0.6 - 2014.09.16
 
 [core]
diff --git a/hardware/arduino/avr/cores/arduino/HardwareSerial.cpp b/hardware/arduino/avr/cores/arduino/HardwareSerial.cpp
index 29a336649..41935e320 100644
--- a/hardware/arduino/avr/cores/arduino/HardwareSerial.cpp
+++ b/hardware/arduino/avr/cores/arduino/HardwareSerial.cpp
@@ -152,7 +152,7 @@ void HardwareSerial::end()
 
 int HardwareSerial::available(void)
 {
-  return (int)(SERIAL_RX_BUFFER_SIZE + _rx_buffer_head - _rx_buffer_tail) % SERIAL_RX_BUFFER_SIZE;
+  return ((unsigned int)(SERIAL_RX_BUFFER_SIZE + _rx_buffer_head - _rx_buffer_tail)) % SERIAL_RX_BUFFER_SIZE;
 }
 
 int HardwareSerial::peek(void)
diff --git a/hardware/arduino/avr/cores/arduino/HardwareSerial.h b/hardware/arduino/avr/cores/arduino/HardwareSerial.h
index 935934b19..7dc2aa98c 100644
--- a/hardware/arduino/avr/cores/arduino/HardwareSerial.h
+++ b/hardware/arduino/avr/cores/arduino/HardwareSerial.h
@@ -32,6 +32,8 @@
 // using a ring buffer (I think), in which head is the index of the location
 // to which to write the next incoming character and tail is the index of the
 // location from which to read.
+// NOTE: a "power of 2" buffer size is reccomended to dramatically
+//       optimize all the modulo operations for ring buffers.
 #if !(defined(SERIAL_TX_BUFFER_SIZE) && defined(SERIAL_RX_BUFFER_SIZE))
 #if (RAMEND < 1000)
 #define SERIAL_TX_BUFFER_SIZE 16