diff --git a/src/pifmrds/rds.h b/src/pifmrds/rds.h
index f289c7e..292035e 100644
--- a/src/pifmrds/rds.h
+++ b/src/pifmrds/rds.h
@@ -24,7 +24,7 @@
 
 #include <stdint.h>
 
-extern void get_rds_samples(float *buffer, int count, int stereo, int ct_clock_enabled, float sample_volume=1.0);
+extern void get_rds_samples(float *buffer, int count, int stereo, int ct_clock_enabled, float sample_volume);
 extern void set_rds_pi(uint16_t pi_code);
 extern void set_rds_rt(char *rt);
 extern void set_rds_ps(char *ps);