diff --git a/SP5WWP/m17-decoder/m17-decoder-sym.c b/SP5WWP/m17-decoder/m17-decoder-sym.c
index 18384a0..1383e2c 100644
--- a/SP5WWP/m17-decoder/m17-decoder-sym.c
+++ b/SP5WWP/m17-decoder/m17-decoder-sym.c
@@ -87,6 +87,7 @@ void decode_callsign(uint8_t *outp, const uint8_t *inp)
 		encoded/=40;
 		i++;
 	}
+	outp[i]=0;
 }
 
 int main(void)