diff --git a/SP5WWP/lib/Makefile b/SP5WWP/lib/Makefile
index 396e9d0..15338ab 100644
--- a/SP5WWP/lib/Makefile
+++ b/SP5WWP/lib/Makefile
@@ -2,7 +2,7 @@ INC     = -I .
 
 TARGET  = libm17.so
 
-CFLAGS  = $(INC) -fPIC -Wall
+CFLAGS  = $(INC) -fPIC -Wall -Wextra
 LDFLAGS = -shared -lm
 SRCS    = $(wildcard *.c) $(wildcard */*.c)
 OBJS    = $(SRCS:.c=.o)
diff --git a/SP5WWP/lib/math/math.c b/SP5WWP/lib/math/math.c
index 95dc1a2..3a24f5f 100644
--- a/SP5WWP/lib/math/math.c
+++ b/SP5WWP/lib/math/math.c
@@ -105,7 +105,10 @@ uint16_t add16(const uint16_t a, const uint16_t b)
  */
 uint16_t sub16(const uint16_t a, const uint16_t b)
 {	
-	return a>=b ? a-b : 0x0000U;
+	if(a>=b)
+		return a-b;
+	else
+		return 0x0000U;
 }
 
 /**
diff --git a/SP5WWP/lib/payload/call.c b/SP5WWP/lib/payload/call.c
index f2a3610..8637c54 100644
--- a/SP5WWP/lib/payload/call.c
+++ b/SP5WWP/lib/payload/call.c
@@ -23,7 +23,7 @@ void decode_callsign_bytes(uint8_t *outp, const uint8_t inp[6])
 
 	//repack the data to a uint64_t
 	for(uint8_t i=0; i<6; i++)
-		encoded|=(uint64_t)inp[5-i]<<(8*i);
+		encoded|=(uint64_t)inp[i]<<(8*i);
 
 	//check if the value is reserved (not a callsign)
 	if(encoded>=262144000000000ULL)