diff --git a/Arduino.mk b/Arduino.mk
index 9e29e37..e48f097 100644
--- a/Arduino.mk
+++ b/Arduino.mk
@@ -736,7 +736,7 @@ ifeq ($(strip $(CHK_SOURCES)),)
                 $(call show_config_info,No .pde or .ino files found. If you are compiling .c or .cpp files then you need to explicitly include Arduino header files)
             else
                 #TODO: Support more than one file. https://github.com/sudar/Arduino-Makefile/issues/49
-                $(error Need exactly one .pde or .ino file. This makefile doesn't support multiple .ino/.pde files yet)
+                $(error Need exactly one .pde or .ino file. This makefile doesn\'t support multiple .ino/.pde files yet)
             endif
         endif
 
@@ -763,6 +763,19 @@ else
     $(call show_config_info,NO_CORE set so core library will not be built,[MANUAL])
 endif
 
+########################################################################
+# Automatically find the libraries needed to compile the sketch
+
+ifndef MAIN_LIBS
+    MAIN_LIBS = $(shell $(ARDMK_DIR)/bin/auto-lib.py $(USER_LIB_PATH) | \
+                sed -ne 's/MAIN_LIBS \(.*\) /\1/p')
+endif
+
+ifndef LIBS_DEPS
+    LIBS_DEPS = $(shell $(ARDMK_DIR)/bin/auto-lib.py $(USER_LIB_PATH) | \
+                sed -ne 's/LIBS_DEPS \(.*\) /\1/p')
+endif
+
 ########################################################################
 # Determine ARDUINO_LIBS automatically
 
@@ -772,8 +785,7 @@ ifndef ARDUINO_LIBS
         $(shell sed -ne "s/^ *\# *include *[<\"]\(.*\)\.h[>\"]/\1/p" $(LOCAL_SRCS)))
     ARDUINO_LIBS += $(filter $(notdir $(wildcard $(ARDUINO_SKETCHBOOK)/libraries/*)), \
         $(shell sed -ne "s/^ *\# *include *[<\"]\(.*\)\.h[>\"]/\1/p" $(LOCAL_SRCS)))
-    ARDUINO_LIBS += $(filter $(notdir $(wildcard $(USER_LIB_PATH)/*)), \
-        $(shell sed -ne "s/^ *\# *include *[<\"]\(.*\)\.h[>\"]/\1/p" $(LOCAL_SRCS)))
+    ARDUINO_LIBS += $(MAIN_LIBS) $(LIBS_DEPS)
 endif
 
 ########################################################################
@@ -989,13 +1001,27 @@ else
     $(call show_config_info,Size utility: Basic (not AVR-aware),[AUTODETECTED])
 endif
 
-ifneq (,$(strip $(ARDUINO_LIBS)))
+ifneq (,$(strip $(MAIN_LIBS)))
     $(call arduino_output,-)
-    $(call show_config_info,ARDUINO_LIBS =)
+    $(call show_config_info,MAIN_LIBS =)
 endif
 
-ifneq (,$(strip $(USER_LIB_NAMES)))
-    $(foreach lib,$(USER_LIB_NAMES),$(call show_config_info,  $(lib),[USER]))
+ifneq (,$(strip $(MAIN_LIBS)))
+    $(foreach lib,$(MAIN_LIBS),$(call show_config_info,  $(lib),[USER]))
+endif
+
+ifneq (,$(strip $(LIBS_DEPS)))
+    $(call arduino_output,-)
+    $(call show_config_info,LIBS_DEPS =)
+endif
+
+ifneq (,$(strip $(LIBS_DEPS)))
+    $(foreach lib,$(LIBS_DEPS),$(call show_config_info,  $(lib),[USER]))
+endif
+
+ifneq (,$(strip $(SYS_LIBS)))
+    $(call arduino_output,-)
+    $(call show_config_info,SYS_LIBS =)
 endif
 
 ifneq (,$(strip $(SYS_LIB_NAMES)))
@@ -1333,7 +1359,7 @@ ifneq ($(strip $(AVRDUDE_ISP_FUSES_POST)),)
 		$(AVRDUDE) $(AVRDUDE_COM_OPTS) $(AVRDUDE_ISP_OPTS) $(AVRDUDE_ISP_FUSES_POST)
 endif
 
-clean:
+clean::
 		$(REMOVE) $(OBJDIR)
 
 size:	$(TARGET_HEX)
diff --git a/HISTORY.md b/HISTORY.md
index 1924534..072e695 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -12,10 +12,10 @@ I tried to give credit whenever possible. If I have missed anyone, kindly add it
 - Add: Add information about overriding system libs (Issue #229). (https://github.com/sej7278)
 - Add: Add information about reporting bugs to the correct project (Issue #231). (https://github.com/sej7278)
 - Fix: Allow the use of CFLAGS_STD and CXXFLAGS_STD and set defaults (Issue #234) (https://github.com/ladislas)
-- Tweak: Remove \$(EXTRA_XXX) variables (Issue #234) (https://github.com/ladislas)
+- Tweak: Remove $(EXTRA_XXX) variables (Issue #234) (https://github.com/ladislas)
 - Add: Add documentation about CFLAGS_STD and CXXFLAGS_STD (Issue #234) (https://github.com/ladislas)
 - Tweak: Update Malefile-example.mk with STD flags (https://github.com/ladislas)
-
+- Add: Allow "make clean" target to be extended (Issue #239). (https://github.com/sej7278)
 
 ### 1.3.4 (2014-07-12)
 - Tweak: Allow spaces in "Serial.begin (....)". (Issue #190) (https://github.com/pdav)
diff --git a/bin/auto-lib.py b/bin/auto-lib.py
new file mode 100755
index 0000000..77d69f6
--- /dev/null
+++ b/bin/auto-lib.py
@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+
+import os
+import re
+import sys
+
+# Set variables
+USER_LIB_PATH = sys.argv[1]
+USER_LIBS = [] ;
+
+includeRegex = re.compile("(?<=^\#include\s[\<\"])(.*)(?=\.h[\>\"])", re.DOTALL|re.M)
+
+MAIN_SRCS = [] ;
+MAIN_LIBS = [] ;
+
+LIBS_DEPS = [] ;
+LIBS_DEPS_STACK = [] ;
+
+# Define functions
+def outputLibs(libArray):
+	for lib in libArray:
+		print(lib),
+	print("")
+
+# Find local sources .ino, .c or .cpp
+for file in os.listdir(os.curdir):
+	if file.endswith((".c", ".cpp", ".ino")):
+		MAIN_SRCS.append(file)
+
+# Find all USER_LIBS
+for path, dirs, files in os.walk(USER_LIB_PATH):
+	for d in dirs:
+		USER_LIBS.append(d)
+
+# Find MAIN_LIBS included in MAIN_SRCS
+for src in MAIN_SRCS:
+	currentFile = open(src)
+	includes = []
+
+	for line in currentFile:
+		match = includeRegex.search(line)
+		if match:
+			if match.group(1) in USER_LIBS:
+				MAIN_LIBS.append(match.group(1))
+
+MAIN_LIBS = list(sorted(MAIN_LIBS))
+
+# Find LIBS_DEPS includes in MAIN_LIBS
+for lib in MAIN_LIBS:
+	if lib in USER_LIBS:
+		currentFile = open(USER_LIB_PATH + "/" + lib + "/" + lib + ".h")
+
+		for line in currentFile:
+			match = includeRegex.search(line)
+			if match:
+				if match.group(1) in USER_LIBS and match.group(1) not in MAIN_LIBS:
+					LIBS_DEPS_STACK.append(match.group(1))
+
+LIBS_DEPS_STACK = sorted(set(LIBS_DEPS_STACK))
+
+# Recursively find all dependencies of every libraries in USER_LIB_PATH
+while LIBS_DEPS_STACK:
+	for lib in LIBS_DEPS_STACK:
+		if lib in USER_LIBS:
+			currentFile = open(USER_LIB_PATH + "/" + lib + "/" + lib + ".h")
+
+			for line in currentFile:
+				match = includeRegex.search(line)
+				if match:
+					if match.group(1) in USER_LIBS and match.group(1) not in LIBS_DEPS_STACK or match.group(1) in LIBS_DEPS and match.group(1) not in MAIN_LIBS:
+						LIBS_DEPS_STACK.append(match.group(1))
+
+				else:
+					LIBS_DEPS.append(lib)
+					if lib in LIBS_DEPS_STACK:
+						LIBS_DEPS_STACK.remove(lib)
+
+	LIBS_DEPS_STACK = sorted(set(LIBS_DEPS_STACK))
+
+LIBS_DEPS = sorted(set(LIBS_DEPS))
+
+# Output libraries for the Makefile
+print("MAIN_LIBS"),
+outputLibs(MAIN_LIBS)
+
+print("LIBS_DEPS"),
+outputLibs(LIBS_DEPS)
diff --git a/examples/MakefileExample/Makefile-example.mk b/examples/MakefileExample/Makefile-example.mk
index 964f9de..67e83e3 100644
--- a/examples/MakefileExample/Makefile-example.mk
+++ b/examples/MakefileExample/Makefile-example.mk
@@ -36,7 +36,7 @@ MONITOR_BAUDRATE  = 115200
 ### On OS X with `homebrew`:
 AVR_TOOLS_DIR     = /usr/local
 ### or on Linux: (remove the one you don't want)
-AVR_TOOLS_DIR     = /usr/bin
+AVR_TOOLS_DIR     = /usr
 
 ### AVRDDUDE
 ### Path to avrdude directory.