diff --git a/src/libopensc/errors.c b/src/libopensc/errors.c
index 0f0fbe7e..e84884d4 100644
--- a/src/libopensc/errors.c
+++ b/src/libopensc/errors.c
@@ -28,8 +28,8 @@ const char *sc_strerror(int error)
 	const char *rdr_errors[] = {
 		"Generic reader error",
 		"No readers found",
-		"Slot not found",
-		"Slot already connected",
+		"Slot not found", /* Not used */
+		"Slot already connected", /* Not used */
 		"Card not present",
 		"Card removed",
 		"Card reset",
@@ -37,11 +37,12 @@ const char *sc_strerror(int error)
 		"Timed out while waiting for user input",
 		"Input operation cancelled by user",
 		"The two PINs did not match",
-		"Message too long (keypad)",
+		"Message too long (keypad)", /* Not used */
 		"Timeout while waiting for event from card reader",
 		"Unresponsive card (correctly inserted?)",
 		"Reader detached (hotplug device?)",
 		"Reader reattached (hotplug device?)",
+		"Reader in use by another application"
 	};
 	const int rdr_base = -SC_ERROR_READER;
 	const char *card_errors[] = {
diff --git a/src/libopensc/errors.h b/src/libopensc/errors.h
index 3362e799..d27d19f1 100644
--- a/src/libopensc/errors.h
+++ b/src/libopensc/errors.h
@@ -31,8 +31,8 @@ extern "C" {
 /* Errors related to reader operation */
 #define SC_ERROR_READER				-1100
 #define SC_ERROR_NO_READERS_FOUND		-1101
-#define SC_ERROR_SLOT_NOT_FOUND			-1102
-#define SC_ERROR_SLOT_ALREADY_CONNECTED		-1103
+#define SC_ERROR_SLOT_NOT_FOUND			-1102 /* FIXME: not used */
+#define SC_ERROR_SLOT_ALREADY_CONNECTED		-1103 /* FIXME: not used */
 #define SC_ERROR_CARD_NOT_PRESENT		-1104
 #define SC_ERROR_CARD_REMOVED			-1105
 #define SC_ERROR_CARD_RESET			-1106
@@ -40,11 +40,12 @@ extern "C" {
 #define SC_ERROR_KEYPAD_TIMEOUT			-1108
 #define SC_ERROR_KEYPAD_CANCELLED		-1109
 #define SC_ERROR_KEYPAD_PIN_MISMATCH		-1110
-#define SC_ERROR_KEYPAD_MSG_TOO_LONG		-1111
+#define SC_ERROR_KEYPAD_MSG_TOO_LONG		-1111 /* FIXME: not used */
 #define SC_ERROR_EVENT_TIMEOUT			-1112
 #define SC_ERROR_CARD_UNRESPONSIVE		-1113
 #define SC_ERROR_READER_DETACHED		-1114
 #define SC_ERROR_READER_REATTACHED		-1115
+#define SC_ERROR_READER_LOCKED			-1116
 
 /* Resulting from a card command or related to the card*/
 #define SC_ERROR_CARD_CMD_FAILED		-1200