Index: boot/Makefile.build
===================================================================
--- boot/Makefile.build	(revision 7b90778d6bd2bbdf6bb7c2d938d4519fdc30bbb9)
+++ boot/Makefile.build	(revision e8c5c116302f5f37cbb1f2d23a2b292a146beb49)
@@ -40,5 +40,5 @@
 	-finput-charset=UTF-8 -ffreestanding -fno-builtin -nostdlib -nostdinc \
 	-Wall -Wextra -Wno-unused-parameter -Wmissing-prototypes \
-	-Werror-implicit-function-declaration -Wwrite-strings \
+	-std=gnu99 -Werror-implicit-function-declaration -Wwrite-strings \
 	-pipe
 
Index: kernel/Makefile
===================================================================
--- kernel/Makefile	(revision 7b90778d6bd2bbdf6bb7c2d938d4519fdc30bbb9)
+++ kernel/Makefile	(revision e8c5c116302f5f37cbb1f2d23a2b292a146beb49)
@@ -94,5 +94,5 @@
 	-fexec-charset=UTF-8 -fwide-exec-charset=UTF-32$(ENDIANESS) \
 	-finput-charset=UTF-8 -ffreestanding -fno-builtin -nostdlib -nostdinc \
-	-Wall -Wextra -Wno-unused-parameter -Wmissing-prototypes \
+	-std=gnu99 -Wall -Wextra -Wno-unused-parameter -Wmissing-prototypes \
 	-Werror-implicit-function-declaration -Wwrite-strings \
 	-pipe
Index: uspace/Makefile.common
===================================================================
--- uspace/Makefile.common	(revision 7b90778d6bd2bbdf6bb7c2d938d4519fdc30bbb9)
+++ uspace/Makefile.common	(revision e8c5c116302f5f37cbb1f2d23a2b292a146beb49)
@@ -155,5 +155,5 @@
 	-finput-charset=UTF-8 -ffreestanding -fno-builtin -nostdlib -nostdinc \
 	-Wall -Wextra -Wno-clobbered -Wno-unused-parameter -Wmissing-prototypes \
-	-Werror-implicit-function-declaration -Wwrite-strings \
+	-std=gnu99 -Werror-implicit-function-declaration -Wwrite-strings \
 	-pipe -g -D__$(ENDIANESS)__