diff --git a/src/rtl_adsb.c b/src/rtl_adsb.c
index 7aea8dd..2f2a773 100644
--- a/src/rtl_adsb.c
+++ b/src/rtl_adsb.c
@@ -370,6 +370,7 @@ int main(int argc, char **argv)
 	int r, opt;
 	int gain = AUTO_GAIN; /* tenths of a dB */
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	int ppm_error = 0;
 	int enable_biastee = 0;
diff --git a/src/rtl_biast.c b/src/rtl_biast.c
index 6018450..df27d82 100644
--- a/src/rtl_biast.c
+++ b/src/rtl_biast.c
@@ -67,6 +67,7 @@ int main(int argc, char **argv)
 {
 	int i, r, opt;
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	uint32_t bias_on = 0;
         uint32_t gpio_pin = 0;
diff --git a/src/rtl_eeprom.c b/src/rtl_eeprom.c
index ca35f67..edf4022 100644
--- a/src/rtl_eeprom.c
+++ b/src/rtl_eeprom.c
@@ -251,6 +251,7 @@ int main(int argc, char **argv)
 {
 	int i, r, opt;
 	uint32_t dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int device_count;
 	char *filename = NULL;
 	FILE *file = NULL;
diff --git a/src/rtl_fm.c b/src/rtl_fm.c
index b163979..019fdf0 100644
--- a/src/rtl_fm.c
+++ b/src/rtl_fm.c
@@ -98,6 +98,7 @@ struct dongle_state
 	pthread_t thread;
 	rtlsdr_dev_t *dev;
 	int      dev_index;
+//	int      rtlsdr_get_index_by_serial(const char *serial);
 	uint32_t freq;
 	uint32_t rate;
 	int      gain;
diff --git a/src/rtl_power.c b/src/rtl_power.c
index 8416176..8c303a1 100644
--- a/src/rtl_power.c
+++ b/src/rtl_power.c
@@ -764,6 +764,7 @@ int main(int argc, char **argv)
 	int f_set = 0;
 	int gain = AUTO_GAIN; // tenths of a dB
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	int ppm_error = 0;
 	int interval = 10;
diff --git a/src/rtl_sdr.c b/src/rtl_sdr.c
index e6537ca..6f2829a 100644
--- a/src/rtl_sdr.c
+++ b/src/rtl_sdr.c
@@ -116,6 +116,7 @@ int main(int argc, char **argv)
 	FILE *file;
 	uint8_t *buffer;
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	uint32_t frequency = 100000000;
 	uint32_t samp_rate = DEFAULT_SAMPLE_RATE;
diff --git a/src/rtl_tcp.c b/src/rtl_tcp.c
index 270e9f6..8bf1086 100644
--- a/src/rtl_tcp.c
+++ b/src/rtl_tcp.c
@@ -372,6 +372,7 @@ int main(int argc, char **argv)
 	struct sockaddr_in local, remote;
 	uint32_t buf_num = 0;
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	int gain = 0;
 	int ppm_error = 0;
diff --git a/src/rtl_test.c b/src/rtl_test.c
index 9b44097..3e58277 100644
--- a/src/rtl_test.c
+++ b/src/rtl_test.c
@@ -310,6 +310,7 @@ int main(int argc, char **argv)
 	int sync_mode = 0;
 	uint8_t *buffer;
 	int dev_index = 0;
+	int rtlsdr_get_index_by_serial(const char *serial);
 	int dev_given = 0;
 	uint32_t out_block_size = DEFAULT_BUF_LENGTH;
 	int count;