diff --git a/conf/Makefile.lpc21 b/conf/Makefile.lpc21
index 180500e6d3..1b7572a066 100644
--- a/conf/Makefile.lpc21
+++ b/conf/Makefile.lpc21
@@ -80,17 +80,19 @@ CINCS = $(INCLUDES) -I$(SRC_ARCH)/include
 CFLAGS = $(CINCS)
 CFLAGS += -O$(OPT)
 # CFLAGS += -malignment-traps
-CFLAGS += -Wall -Wcast-qual -Wimplicit -Wcast-align
-CFLAGS += -Wpointer-arith -Wswitch
-CFLAGS += -Wredundant-decls -Wreturn-type -Wshadow -Wunused
 CFLAGS += -Wa,-adhlns=$(OBJDIR)/$(notdir $(subst $(suffix $<),.lst,$<))
 CFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))
 CFLAGS += -ffunction-sections -fdata-sections
 CFLAGS += -finline-limit=1200 --param inline-unit-growth=100
 
-# flags only for C
+# flags for warnings
+CFLAGS += -Wall -Wextra
+CFLAGS += -Wcast-qual -Wimplicit -Wcast-align
+CFLAGS += -Wpointer-arith -Wswitch
+CFLAGS += -Wredundant-decls -Wreturn-type -Wshadow -Wunused
 CFLAGS += -Wstrict-prototypes -Wmissing-declarations
 CFLAGS += -Wmissing-prototypes -Wnested-externs
+
 CFLAGS += $(CSTANDARD)
 CFLAGS += $($(TARGET).CFLAGS) $(LOCAL_CFLAGS)
 
diff --git a/conf/Makefile.stm32 b/conf/Makefile.stm32
index ef06858e07..dbaa295925 100644
--- a/conf/Makefile.stm32
+++ b/conf/Makefile.stm32
@@ -98,7 +98,7 @@ $(info Using "$($(TARGET).LDSCRIPT)" as ldscript for target "$(TARGET)".)
 endif
 endif
 
-CFLAGS = -I. -I./$(ARCH) -I../ext/libopencm3/include $(INCLUDES) -D__thumb2__ -Wall -msoft-float -O$(OPT)
+CFLAGS = -I. -I./$(ARCH) -I../ext/libopencm3/include $(INCLUDES) -D__thumb2__ -msoft-float -O$(OPT)
 CFLAGS += -Wl,--gc-sections
 CFLAGS += -mfix-cortex-m3-ldrd
 CFLAGS += -mcpu=$(MCU) -mthumb -ansi
@@ -107,16 +107,20 @@ CFLAGS += -std=gnu99
 CFLAGS += -fno-common
 CFLAGS += -g$(DEBUG)
 CFLAGS += -ffunction-sections -fdata-sections
+
+# flags for warnings
+CFLAGS += -Wall -Wextra
 CFLAGS += -Wimplicit
 CFLAGS += -Wcast-align
 CFLAGS += -Wpointer-arith -Wswitch
 CFLAGS += -Wredundant-decls -Wreturn-type -Wshadow -Wunused
-CFLAGS += -Wa,-adhlns=$(OBJDIR)/$(notdir $(subst $(suffix $<),.lst,$<))
 CFLAGS += -Wnested-externs
 CFLAGS += -Wmissing-prototypes
 CFLAGS += -Wstrict-prototypes
 CFLAGS += -Wmissing-declarations
 CFLAGS += -Wswitch-default
+
+CFLAGS += -Wa,-adhlns=$(OBJDIR)/$(notdir $(subst $(suffix $<),.lst,$<))
 CFLAGS += -DSTM32F1
 
 CFLAGS += $($(TARGET).CFLAGS)
diff --git a/sw/airborne/lisa/plug_sys.c b/sw/airborne/lisa/plug_sys.c
index 170393a124..e3901255c6 100644
--- a/sw/airborne/lisa/plug_sys.c
+++ b/sw/airborne/lisa/plug_sys.c
@@ -14,11 +14,11 @@ extern ssize_t                _write(int, const void *, size_t);
 extern int                    _close(int);
 extern ssize_t                _read(int, void *, size_t);
 
-off_t                  _lseek(int a, off_t b, int c) { return b;}
+off_t                  _lseek(int a __attribute__((unused)), off_t b, int c __attribute__((unused))) { return b;}
 void                   abort(void) {while(1){};}
 pid_t                  getpid(void) { return 0;}
-int                    kill(pid_t a, int b) {return 0;}
-void *                 _sbrk(int a) {return 0;}
-ssize_t                _write(int a, const void *b, size_t c) {return 0; }
-int                    _close(int a) { return 0;}
-ssize_t                _read(int a, void *b, size_t c) {return 0;}
+int                    kill(pid_t a __attribute__((unused)), int b __attribute__((unused))) {return 0;}
+void *                 _sbrk(int a __attribute__((unused))) {return 0;}
+ssize_t                _write(int a __attribute__((unused)), const void *b __attribute__((unused)), size_t c __attribute__((unused))) {return 0; }
+int                    _close(int a __attribute__((unused))) { return 0;}
+ssize_t                _read(int a __attribute__((unused)), void *b __attribute__((unused)), size_t c __attribute__((unused))) {return 0;}