Index: boot/Makefile.build
===================================================================
--- boot/Makefile.build	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ boot/Makefile.build	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -35,4 +35,6 @@
 
 DEFS = -DBOOT -DRELEASE=$(RELEASE) "-DCOPYRIGHT=$(COPYRIGHT)" "-DNAME=$(NAME)" -D__$(BITS)_BITS__ -D__$(ENDIANESS)__
+
+LFLAGS = --fatal-warnings
 
 GCC_CFLAGS = -I$(INCLUDES) -O$(OPTIMIZATION) -imacros $(CONFIG_HEADER) \
Index: kernel/Makefile
===================================================================
--- kernel/Makefile	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ kernel/Makefile	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -128,6 +128,6 @@
 # AFLAGS and LFLAGS must be initialized before the inclusion.
 #
-AFLAGS =
-LFLAGS = -n -T $(LINK) -M
+AFLAGS = --fatal-warnings
+LFLAGS = -n -T $(LINK) -M --fatal-warnings
 
 #
Index: uspace/Makefile.common
===================================================================
--- uspace/Makefile.common	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ uspace/Makefile.common	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -161,4 +161,7 @@
 LIBURCU_PREFIX = $(LIB_PREFIX)/urcu
 
+AFLAGS = --fatal-warnings
+LFLAGS = --fatal-warnings
+
 ifeq ($(STATIC_NEEDED),y)
 	STATIC_BUILD = y
@@ -201,5 +204,5 @@
 else
 	BASE_LIBS = $(LIBC_PREFIX)/libc.so0 $(LIBSOFTINT_PREFIX)/libsofti.so0
-	LFLAGS = -Bdynamic
+	LFLAGS += -Bdynamic
 	LINKER_SCRIPT ?= $(LIBC_PREFIX)/arch/$(UARCH)/_link-dlexe.ld
 	ifeq ($(MATH),y)
Index: uspace/lib/c/arch/ppc32/Makefile.common
===================================================================
--- uspace/lib/c/arch/ppc32/Makefile.common	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ uspace/lib/c/arch/ppc32/Makefile.common	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -36,5 +36,5 @@
 GCC_CFLAGS += -mcpu=powerpc -m$(FLOATS)-float -m32
 BASE_LIBS += $(LIBSOFTFLOAT_PREFIX)/libsoftfloat.a
-AFLAGS = -a32
+AFLAGS += -a32
 
 ENDIANESS = BE
Index: uspace/lib/c/arch/sparc32/Makefile.common
===================================================================
--- uspace/lib/c/arch/sparc32/Makefile.common	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ uspace/lib/c/arch/sparc32/Makefile.common	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -27,5 +27,5 @@
 #
 
-LFLAGS = -no-check-sections
+LFLAGS += -no-check-sections
 
 ENDIANESS = BE
Index: uspace/lib/c/arch/sparc64/Makefile.common
===================================================================
--- uspace/lib/c/arch/sparc64/Makefile.common	(revision c190b34905f4efa4aa7c42aaf88c5dd2468484d2)
+++ uspace/lib/c/arch/sparc64/Makefile.common	(revision ae7bbfd0bcf872d80ac6f3f37faf7fa216782613)
@@ -35,5 +35,5 @@
 GCC_CFLAGS += -m64 -mcmodel=medlow
 
-LFLAGS = -no-check-sections
+LFLAGS += -no-check-sections
 
 ENDIANESS = BE