diff --git a/src/libopensc/card.c b/src/libopensc/card.c
index 69e9ce54..d38c6a21 100644
--- a/src/libopensc/card.c
+++ b/src/libopensc/card.c
@@ -447,7 +447,7 @@ int sc_read_binary(sc_card_t *card, unsigned int idx,
 int sc_write_binary(sc_card_t *card, unsigned int idx,
 		    const u8 *buf, size_t count, unsigned long flags)
 {
-	size_t max_lc = card->max_send_size;
+	size_t max_lc = card->max_send_size > 0 ? card->max_send_size : 255;
 	int r;
 
 	assert(card != NULL && card->ops != NULL && buf != NULL);
@@ -489,7 +489,7 @@ int sc_write_binary(sc_card_t *card, unsigned int idx,
 int sc_update_binary(sc_card_t *card, unsigned int idx,
 		     const u8 *buf, size_t count, unsigned long flags)
 {
-	size_t max_lc = card->max_send_size;
+	size_t max_lc = card->max_send_size > 0 ? card->max_send_size : 255;
 	int r;
 
 	assert(card != NULL && card->ops != NULL && buf != NULL);
diff --git a/src/libopensc/iso7816.c b/src/libopensc/iso7816.c
index 0fb5cad6..089d7646 100644
--- a/src/libopensc/iso7816.c
+++ b/src/libopensc/iso7816.c
@@ -119,7 +119,7 @@ static int iso7816_read_binary(sc_card_t *card,
 		return SC_ERROR_OFFSET_TOO_LARGE;
 	}
 
-	assert(count <= card->max_recv_size);
+	assert(count <= (card->max_recv_size > 0 ? card->max_recv_size : 256));
 	sc_format_apdu(card, &apdu, SC_APDU_CASE_2_SHORT, 0xB0,
 		       (idx >> 8) & 0x7F, idx & 0xFF);
 	apdu.le = count;
@@ -247,7 +247,7 @@ static int iso7816_write_binary(sc_card_t *card,
 	sc_apdu_t apdu;
 	int r;
 
-	assert(count <= card->max_send_size);
+	assert(count <= (card->max_send_size > 0 ? card->max_send_size : 255));
 
 	if (idx > 0x7fff) {
 		sc_debug(card->ctx, SC_LOG_DEBUG_NORMAL, "invalid EF offset: 0x%X > 0x7FFF", idx);
@@ -274,7 +274,7 @@ static int iso7816_update_binary(sc_card_t *card,
 	sc_apdu_t apdu;
 	int r;
 
-	assert(count <= card->max_send_size);
+	assert(count <= (card->max_send_size > 0 ? card->max_send_size : 255));
 
 	if (idx > 0x7fff) {
 		sc_debug(card->ctx, SC_LOG_DEBUG_NORMAL, "invalid EF offset: 0x%X > 0x7FFF", idx);
diff --git a/src/libopensc/muscle.h b/src/libopensc/muscle.h
index 260d3098..fa0f62d7 100644
--- a/src/libopensc/muscle.h
+++ b/src/libopensc/muscle.h
@@ -32,8 +32,8 @@
 #define MSC_MAX_PIN_COMMAND_LENGTH ((1 + MSC_MAX_PIN_LENGTH) * 2)
 
 /* Currently max size handled by muscle driver is 255 ... */
-#define MSC_MAX_READ (MIN(card->reader->driver->max_recv_size,255))
-#define MSC_MAX_SEND (MIN(card->reader->driver->max_send_size,255))
+#define MSC_MAX_READ (card->max_recv_size > 0 ? card->max_recv_size : 255)
+#define MSC_MAX_SEND (card->max_send_size > 0 ? card->max_send_size : 255)
 
 int msc_list_objects(sc_card_t* card, u8 next, mscfs_file_t* file);
 int msc_partial_read_object(sc_card_t *card, msc_id objectId, int offset, u8 *data, size_t dataLength);