diff --git a/bin2c.c b/bin2c.c
index 2fba5bd..23af1bd 100644
--- a/bin2c.c
+++ b/bin2c.c
@@ -39,7 +39,7 @@ int main(int argc, char * argv[])
 	fprintf(fp_out, "/* Automatically generated file from %s */\n", argv[1]);
 	strcpy(fname, argv[1]);
 	for(p = fname; *p; p++)
-		if(!isalnum(*p))
+		if(!isalnum((int) *p))
 			*p = '_';
 	fprintf(fp_out, "unsigned int %s_len = %d;\n", fname, length);
 	fprintf(fp_out, "unsigned char %s[] = {\n\t", fname);
diff --git a/main.c b/main.c
index bee9fbe..ed5c31f 100644
--- a/main.c
+++ b/main.c
@@ -587,7 +587,8 @@ int file_server(libusb_device_handle * usb_device)
 					file_size = ftell(fp);
 					fseek(fp, 0, SEEK_SET);
 
-					if(verbose) printf("File size = %d bytes\n", file_size);
+					if(verbose || !file_size)
+						printf("File size = %d bytes\n", file_size);
 
 					int sz = libusb_control_transfer(usb_device, LIBUSB_REQUEST_TYPE_VENDOR, 0,
 					    file_size & 0xffff, file_size >> 16, NULL, 0, 1000);
@@ -598,7 +599,7 @@ int file_server(libusb_device_handle * usb_device)
 				else
 				{
 					ep_write(NULL, 0, usb_device);
-					if(verbose) printf("Cannot open file %s\n", message.fname);
+					printf("Cannot open file %s\n", message.fname);
 					break;
 				}
 				break;
@@ -615,6 +616,9 @@ int file_server(libusb_device_handle * usb_device)
 					file_size = ftell(fp);
 					fseek(fp, 0, SEEK_SET);
 
+					if (!file_size)
+						printf("WARNING: %s is empty\n", message.fname);
+
 					buf = malloc(file_size);
 					if(buf == NULL)
 					{