diff --git a/common.mk b/common.mk
index 62ac0ff7..1cffc3cc 100644
--- a/common.mk
+++ b/common.mk
@@ -9,6 +9,7 @@ SRC +=	$(COMMON_DIR)/host.c \
 	$(COMMON_DIR)/keymap.c \
 	$(COMMON_DIR)/timer.c \
 	$(COMMON_DIR)/print.c \
+	$(COMMON_DIR)/debug.c \
 	$(COMMON_DIR)/bootloader.c \
 	$(COMMON_DIR)/suspend.c \
 	$(COMMON_DIR)/xprintf.S \
diff --git a/common/debug.c b/common/debug.c
new file mode 100644
index 00000000..c4fa3a05
--- /dev/null
+++ b/common/debug.c
@@ -0,0 +1,12 @@
+#include <stdbool.h>
+#include "debug.h"
+
+
+//debug_config_t debug_config = { .enable = false, .matrix = false };
+debug_config_t debug_config = {
+    .enable = false,
+    .matrix = false,
+    .keyboard = false,
+    .mouse = false,
+};
+
diff --git a/common/debug_config.h b/common/debug_config.h
index e00fd103..43e4c5c5 100644
--- a/common/debug_config.h
+++ b/common/debug_config.h
@@ -36,7 +36,7 @@ typedef union {
         uint8_t reserved:4;
     };
 } debug_config_t;
-debug_config_t debug_config;
+extern debug_config_t debug_config;
 
 /* for backward compatibility */
 #define debug_enable    (debug_config.enable)
diff --git a/common/host.h b/common/host.h
index a56e6c3b..918af69e 100644
--- a/common/host.h
+++ b/common/host.h
@@ -32,8 +32,8 @@ extern "C" {
 extern bool keyboard_nkro;
 #endif
 
-uint8_t keyboard_idle;
-uint8_t keyboard_protocol;
+extern uint8_t keyboard_idle;
+extern uint8_t keyboard_protocol;
 
 
 /* host driver */
diff --git a/common/print.h b/common/print.h
index 930e84be..77993289 100644
--- a/common/print.h
+++ b/common/print.h
@@ -34,10 +34,7 @@
 
 // this macro allows you to write print("some text") and
 // the string is automatically placed into flash memory :)
-// TODO: avoid collision with arduino/Print.h
-#ifndef __cplusplus
 #define print(s)                print_P(PSTR(s))
-#endif
 #define println(s)              print_P(PSTR(s "\n"))
 
 /* for old name */
diff --git a/common/xprintf.h b/common/xprintf.h
index f58bca81..59c6f253 100644
--- a/common/xprintf.h
+++ b/common/xprintf.h
@@ -8,6 +8,10 @@
 #include <inttypes.h>
 #include <avr/pgmspace.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 extern void (*xfunc_out)(uint8_t);
 #define xdev_out(func) xfunc_out = (void(*)(uint8_t))(func)
 
@@ -99,5 +103,9 @@ char xatoi(char **str, long *ret);
     Pointer to return value
 */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
 
diff --git a/protocol/usb_hid/arduino-1.0.1/cores/arduino/WString.h b/protocol/usb_hid/arduino-1.0.1/cores/arduino/WString.h
index d76d2a33..947325e5 100644
--- a/protocol/usb_hid/arduino-1.0.1/cores/arduino/WString.h
+++ b/protocol/usb_hid/arduino-1.0.1/cores/arduino/WString.h
@@ -35,7 +35,7 @@
 //     -std=c++0x
 
 class __FlashStringHelper;
-#define F(string_literal) (reinterpret_cast<__FlashStringHelper *>(PSTR(string_literal)))
+#define F(string_literal) (reinterpret_cast<const __FlashStringHelper *>(PSTR(string_literal)))
 
 // An inherited class for holding the result of a concatenation.  These
 // result objects are assumed to be writable by subsequent concatenations.
diff --git a/protocol/usb_hid/override_wiring.c b/protocol/usb_hid/override_wiring.c
index 3b3f5e30..1e9a94ce 100644
--- a/protocol/usb_hid/override_wiring.c
+++ b/protocol/usb_hid/override_wiring.c
@@ -1,6 +1,7 @@
 /*
  * To keep Timer0 for common/timer.c override arduino/wiring.c.
  */
+#define __DELAY_BACKWARD_COMPATIBLE__
 #include <util/delay.h>
 #include "common/timer.h"
 #include "Arduino.h"
diff --git a/protocol/usb_hid/parser.cpp b/protocol/usb_hid/parser.cpp
index 66e94951..28151f9d 100644
--- a/protocol/usb_hid/parser.cpp
+++ b/protocol/usb_hid/parser.cpp
@@ -1,5 +1,3 @@
-#include <cstring.h>
-
 #include "parser.h"
 #include "usb_hid.h"