diff --git a/channels/smartcard/client/smartcard_operations.c b/channels/smartcard/client/smartcard_operations.c
index 759085d41..fcc326200 100644
--- a/channels/smartcard/client/smartcard_operations.c
+++ b/channels/smartcard/client/smartcard_operations.c
@@ -457,7 +457,7 @@ static DWORD filter_device_by_name_a(wLinkedList* list, LPSTR* mszReaders, DWORD
 {
 	size_t rpos = 0, wpos = 0;
 
-	if (LinkedList_Count(list) < 1)
+	if (*mszReaders == NULL || LinkedList_Count(list) < 1)
 		return cchReaders;
 
 	do
@@ -547,9 +547,6 @@ static LONG smartcard_ListReadersA_Call(SMARTCARD_DEVICE* smartcard, SMARTCARD_O
 	cchReaders = SCARD_AUTOALLOCATE;
 	status = ret.ReturnCode = SCardListReadersA(operation->hContext, (LPCSTR) call->mszGroups,
 	                          (LPSTR) &mszReaders, &cchReaders);
-	cchReaders = filter_device_by_name_a(smartcard->names, &mszReaders, cchReaders);
-	ret.msz = (BYTE*) mszReaders;
-	ret.cBytes = cchReaders;
 
 	if (call->mszGroups)
 	{
@@ -563,6 +560,9 @@ static LONG smartcard_ListReadersA_Call(SMARTCARD_DEVICE* smartcard, SMARTCARD_O
 		return status;
 	}
 
+	cchReaders = filter_device_by_name_a(smartcard->names, &mszReaders, cchReaders);
+	ret.msz = (BYTE*) mszReaders;
+	ret.cBytes = cchReaders;
 	smartcard_trace_list_readers_return(smartcard, &ret, FALSE);
 
 	if ((status = smartcard_pack_list_readers_return(smartcard, irp->output, &ret)))
@@ -610,9 +610,6 @@ static LONG smartcard_ListReadersW_Call(SMARTCARD_DEVICE* smartcard, SMARTCARD_O
 	cchReaders = SCARD_AUTOALLOCATE;
 	status = ret.ReturnCode = SCardListReadersW(operation->hContext,
 	                          (LPCWSTR) call->mszGroups, (LPWSTR) &mszReaders, &cchReaders);
-	cchReaders = filter_device_by_name_w(smartcard->names, &mszReaders, cchReaders);
-	ret.msz = (BYTE*) mszReaders;
-	ret.cBytes = cchReaders * 2;
 
 	if (call->mszGroups)
 	{
@@ -626,6 +623,9 @@ static LONG smartcard_ListReadersW_Call(SMARTCARD_DEVICE* smartcard, SMARTCARD_O
 		return status;
 	}
 
+	cchReaders = filter_device_by_name_w(smartcard->names, &mszReaders, cchReaders);
+	ret.msz = (BYTE*) mszReaders;
+	ret.cBytes = cchReaders * 2;
 	smartcard_trace_list_readers_return(smartcard, &ret, TRUE);
 
 	if ((status = smartcard_pack_list_readers_return(smartcard, irp->output, &ret)))