diff --git a/backend/library.c b/backend/library.c
index c51dd13e..4eafd0f9 100644
--- a/backend/library.c
+++ b/backend/library.c
@@ -778,7 +778,7 @@ int ZBarcode_Encode_from_File(struct zint_symbol *symbol, char *filename)
 	FILE *file;
 	unsigned char *buffer;
 	unsigned long fileLen;
-	unsigned char used_characters[255];
+	unsigned char used_characters[256];
 
 	file = fopen(filename, "rb");
 	if (!file) {