diff --git a/software/bios/tftp.c b/software/bios/tftp.c
index ca50034ad..8e255b0f0 100644
--- a/software/bios/tftp.c
+++ b/software/bios/tftp.c
@@ -44,7 +44,7 @@ static int format_ack(unsigned char *buf, unsigned short block)
 static unsigned char *packet_data;
 static int total_length;
 static int transfer_finished;
-static char *dst_buffer;
+static unsigned char *dst_buffer;
 
 static void rx_callback(unsigned int src_ip, unsigned short src_port,
     unsigned short dst_port, void *_data, unsigned int length)
@@ -78,7 +78,7 @@ static void rx_callback(unsigned int src_ip, unsigned short src_port,
 	}
 }
 
-int tftp_get(unsigned int ip, const char *filename, char *buffer)
+int tftp_get(unsigned int ip, const char *filename, void *buffer)
 {
 	int len;
 	int tries;
diff --git a/software/bios/tftp.h b/software/bios/tftp.h
index b27fb50f7..53a6cba69 100644
--- a/software/bios/tftp.h
+++ b/software/bios/tftp.h
@@ -1,7 +1,7 @@
 #ifndef __TFTP_H
 #define __TFTP_H
 
-int tftp_get(unsigned int ip, const char *filename, char *buffer);
+int tftp_get(unsigned int ip, const char *filename, void *buffer);
 
 #endif /* __TFTP_H */