diff --git a/firmware/common/rffc5071.c b/firmware/common/rffc5071.c
index 161e74ec..05a63506 100644
--- a/firmware/common/rffc5071.c
+++ b/firmware/common/rffc5071.c
@@ -130,6 +130,40 @@ void rffc5071_setup(rffc5071_driver_t* const drv)
 	rffc5071_regs_commit(drv);
 }
 
+void rffc5071_lock_test(rffc5071_driver_t* const drv)
+{
+	bool lock = false;
+
+	for (int i = 0; i < NUM_LOCK_ATTEMPTS; i++) {
+		// Tune to 100MHz.
+		rffc5071_set_frequency(drv, 100000000);
+
+		// Wait 1ms.
+		delay_us_at_mhz(1000, 204);
+
+		// Check for lock.
+		lock = rffc5071_check_lock(drv);
+
+		selftest.mixer_locks[i] = lock;
+	}
+
+	// The last attempt must be successful.
+	if (!lock) {
+		selftest.report.pass = false;
+	}
+}
+
+bool rffc5071_check_lock(rffc5071_driver_t* const drv)
+{
+#ifdef PRALINE
+	return gpio_read(drv->gpio_ld);
+#else
+	set_RFFC5071_READSEL(drv, 0b0001);
+	rffc5071_regs_commit(drv);
+	return !!(rffc5071_reg_read(drv, RFFC5071_READBACK_REG) & 0x8000);
+#endif
+}
+
 static uint16_t rffc5071_spi_read(rffc5071_driver_t* const drv, uint8_t r)
 {
 	(void) drv;
diff --git a/firmware/common/rffc5071.h b/firmware/common/rffc5071.h
index 1586e285..164f6324 100644
--- a/firmware/common/rffc5071.h
+++ b/firmware/common/rffc5071.h
@@ -44,6 +44,7 @@ typedef struct {
 /* Initialize chip. Call _setup() externally, as it calls _init(). */
 extern void rffc5071_init(rffc5071_driver_t* const drv);
 extern void rffc5071_setup(rffc5071_driver_t* const drv);
+extern void rffc5071_lock_test(rffc5071_driver_t* const drv);
 
 /* Read a register via SPI. Save a copy to memory and return
  * value. Discard any uncommited changes and mark CLEAN. */
@@ -73,5 +74,6 @@ extern void rffc5071_set_gpo(rffc5071_driver_t* const drv, uint8_t);
 #ifdef PRALINE
 extern bool rffc5071_poll_ld(rffc5071_driver_t* const drv, uint8_t* prelock_state);
 #endif
+extern bool rffc5071_check_lock(rffc5071_driver_t* const drv);
 
 #endif // __RFFC5071_H
diff --git a/firmware/common/selftest.h b/firmware/common/selftest.h
index 0e57d626..86ee2213 100644
--- a/firmware/common/selftest.h
+++ b/firmware/common/selftest.h
@@ -25,6 +25,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#define NUM_LOCK_ATTEMPTS 3
+
 enum {
 	FAILED = 0,
 	PASSED = 1,
@@ -36,6 +38,9 @@ typedef uint8_t test_result_t;
 
 typedef struct {
 	uint16_t mixer_id;
+#ifndef RAD1O
+	bool mixer_locks[NUM_LOCK_ATTEMPTS];
+#endif
 #ifdef PRALINE
 	uint16_t max2831_mux_rssi_1;
 	uint16_t max2831_mux_temp;
diff --git a/firmware/hackrf_usb/hackrf_usb.c b/firmware/hackrf_usb/hackrf_usb.c
index a3f38149..0b5d303a 100644
--- a/firmware/hackrf_usb/hackrf_usb.c
+++ b/firmware/hackrf_usb/hackrf_usb.c
@@ -338,6 +338,10 @@ int main(void)
 
 	rf_path_init(&rf_path);
 
+#ifndef RAD1O
+	rffc5071_lock_test(&mixer);
+#endif
+
 #ifdef PRALINE
 	fpga_if_xcvr_selftest();
 #endif
diff --git a/firmware/hackrf_usb/usb_api_selftest.c b/firmware/hackrf_usb/usb_api_selftest.c
index 1bafbe00..16a1cff4 100644
--- a/firmware/hackrf_usb/usb_api_selftest.c
+++ b/firmware/hackrf_usb/usb_api_selftest.c
@@ -83,6 +83,17 @@ void generate_selftest_report(void)
 	append(&s, &c, itoa(selftest.mixer_id >> 3, 10));
 	append(&s, &c, ", Rev: ");
 	append(&s, &c, itoa(selftest.mixer_id & 0x7, 10));
+	append(&s, &c, ", Locks: ");
+	bool lock;
+	for (int i = 0; i < NUM_LOCK_ATTEMPTS; i++) {
+		lock = selftest.mixer_locks[i];
+		append(&s, &c, itoa(lock, 2));
+	}
+	if (lock) {
+		append(&s, &c, " (PASS)");
+	} else {
+		append(&s, &c, " (FAIL)");
+	}
 	append(&s, &c, "\n");
 #endif
 	append(&s, &c, "Clock: Si5351");