diff --git a/include/libsigrok/libsigrok.h b/include/libsigrok/libsigrok.h
index 34a8df4a..983ddc06 100644
--- a/include/libsigrok/libsigrok.h
+++ b/include/libsigrok/libsigrok.h
@@ -946,9 +946,6 @@ enum sr_configkey {
 	/** Measured quantity. */
 	SR_CONF_MEASURED_QUANTITY,
 
-	/** Measured secondary quantity. */
-	SR_CONF_MEASURED_2ND_QUANTITY,
-
 	/** Equivalent circuit model. */
 	SR_CONF_EQUIV_CIRCUIT_MODEL,
 
diff --git a/src/hwdriver.c b/src/hwdriver.c
index fa730a97..c5d4bf29 100644
--- a/src/hwdriver.c
+++ b/src/hwdriver.c
@@ -167,8 +167,6 @@ static struct sr_key_info sr_key_info_config[] = {
 		"Output frequency target", NULL},
 	{SR_CONF_MEASURED_QUANTITY, SR_T_MQ, "measured_quantity",
 		"Measured quantity", NULL},
-	{SR_CONF_MEASURED_2ND_QUANTITY, SR_T_STRING, "measured_2nd_quantity",
-		"Measured secondary quantity", NULL},
 	{SR_CONF_EQUIV_CIRCUIT_MODEL, SR_T_STRING, "equiv_circuit_model",
 		"Equivalent circuit model", NULL},
 	{SR_CONF_OVER_TEMPERATURE_PROTECTION_ACTIVE, SR_T_BOOL, "otp_active",