diff --git a/Makefile b/Makefile
index 1fb1411..e60ad49 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 #          a look to the 'build.sh' script !       #
 ####################################################
 
-COPT = -Wall -fpic -g -pg  -no-pie -DDEBUG_LEVEL=0
+COPT = -Wall -Wextra -fpic -g -pg  -no-pie -DDEBUG_LEVEL=0
 LDOPT = libfloatimg.a -pg -lm 
 
 all:	essai
diff --git a/experiment/Makefile b/experiment/Makefile
index 0dd4f03..ff6a6a6 100644
--- a/experiment/Makefile
+++ b/experiment/Makefile
@@ -3,7 +3,7 @@
 #  some ugly experiments, do not use in production
 #
 
-COPT = -Wall -fpic -g -DDEBUG_LEVEL=1 -lm
+COPT = -Wall -Wextra -fpic -g -DDEBUG_LEVEL=1 -lm
 DEPS = ../floatimg.h  ../libfloatimg.a Makefile
 LIBS = ../libfloatimg.a -ltiff -lpnglite -lcfitsio -lm
 
diff --git a/experiment/muxplanes.c b/experiment/muxplanes.c
index eca36f0..f52b0d5 100644
--- a/experiment/muxplanes.c
+++ b/experiment/muxplanes.c
@@ -11,7 +11,7 @@
 
 int		verbosity;
 
-/* ---------------------------------------------- ~~~~~~~~~~~~~~~~ */
+/* --------------------------------------------------------------- */
 
 int triplane_muxer(FloatImg *sr, FloatImg *sg, FloatImg *sb,
 					FloatImg *dst, int flages)
@@ -40,7 +40,7 @@ memcpy(dst->B, sb->B, sz);
 
 return 0;
 }
-/* ---------------------------------------------- ~~~~~~~~~~~~~~~~ */
+/* --------------------------------------------------------------- */
 int try_this_muxplane(char *fr, char *fg, char *fb, char *dst, int flags)
 {
 int		foo;
@@ -72,14 +72,18 @@ if (foo) {
 	return foo;
 	}
 
-fimg_export_picture(&dest, dst, 0);
+foo = fimg_export_picture(&dest, dst, 0);
+if (foo) {
+	fprintf(stderr, "%s: err %d exporting to %s\n", __func__, foo, dst);
+	return foo;
+	}
 
 fimg_destroy(&imr);		fimg_destroy(&img);
-fimg_destroy(&imr);		fimg_destroy(&dest);
+fimg_destroy(&imb);		fimg_destroy(&dest);
 
 return 0;
 }
-/* ---------------------------------------------- ~~~~~~~~~~~~~~~~ */
+/* --------------------------------------------------------------- */
 int main(int argc, char *argv[])
 {
 int		foo;
@@ -90,6 +94,11 @@ if (5 != argc) {
 	return 1;
 	}
 
+/*
+ *	and now, we have to decipher options on the
+ *	command line.
+ */
+
 foo = try_this_muxplane(argv[1], argv[2], argv[3], argv[4], 0);
 if (foo) {
 	fprintf(stderr, "oups %d\n", foo);
@@ -98,4 +107,4 @@ if (foo) {
 
 return 0;
 }
-/* ---------------------------------------------- ~~~~~~~~~~~~~~~~ */
+/* --------------------------------------------------------------- */
diff --git a/funcs/Makefile b/funcs/Makefile
index 400aa90..584edc8 100644
--- a/funcs/Makefile
+++ b/funcs/Makefile
@@ -3,7 +3,7 @@
 #		Please, use the 'Gloabl.makefile' system !
 
 
-COPT = -Wall -fpic -g -no-pie  -DDEBUG_LEVEL=0
+COPT = -Wall -Wextra -fpic -g -no-pie  -DDEBUG_LEVEL=0
 DEPS = ../floatimg.h Makefile
 
 OBJS = fimg-png.o fimg-tiff.o misc-plots.o filtrage.o utils.o	\
diff --git a/lib/Makefile b/lib/Makefile
index 0f3dfea..7a9a06f 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -2,7 +2,7 @@
 #	building the base library
 #
 
-COPT = -Wall -fpic -g   -no-pie -DDEBUG_LEVEL=0
+COPT = -Wall -Wextra -fpic -g   -no-pie -DDEBUG_LEVEL=0
 
 OBJS = fimg-core.o fimg-pnm.o fimg-file.o fimg-math.o	\
 	fimg-timers.o operators.o fimg-2gray.o		\
diff --git a/tools/Makefile b/tools/Makefile
index 15c0db8..b16889f 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -5,7 +5,7 @@
 #	PLEASE ! update to the 'Global.makefile' concept !
 #
 
-COPT = -Wall -fpic -g -DDEBUG_LEVEL=0
+COPT = -Wall -Wextra -fpic -g -DDEBUG_LEVEL=0
 DEPS = ../floatimg.h  ../libfloatimg.a Makefile
 
 # 			----------