Index: kernel/Makefile
===================================================================
--- kernel/Makefile	(revision b639d569d5f3a960f411e38bd76a17acdb0cda5f)
+++ kernel/Makefile	(revision d4da8601eeecd6ff5bc2be80760523864c341a26)
@@ -84,5 +84,5 @@
 COMMON_CFLAGS = $(INCLUDES_FLAGS) -O$(OPTIMIZATION) -imacros $(CONFIG_HEADER) \
 	-ffreestanding -fno-builtin -nostdlib -nostdinc \
-	-fexec-charset=UTF-8 -finput-charset=UTF-8
+	-fexec-charset=UTF-8 -finput-charset=UTF-8 -fno-common
 
 GCC_CFLAGS = -std=gnu99 -Wall -Wextra -Wno-unused-parameter \
@@ -112,5 +112,5 @@
 #
 AFLAGS =
-LFLAGS = -n -T $(LINK) -M --fatal-warnings
+LFLAGS = -n -T $(LINK) -M --fatal-warnings --warn-common
 
 # FIXME: This condition is a workaround for issues #693 and #694.