diff --git a/src/libglacier.c b/src/libglacier.c
index daf9ec7..71139e4 100644
--- a/src/libglacier.c
+++ b/src/libglacier.c
@@ -566,13 +566,13 @@ prepare_pkg(char PACKAGE[])
 		char buffer[BUFFER_SIZE];
 		size_t bytes_read;
 
-		pkg_old = fopen(PACKAGE, "r");
+		pkg_old = fopen(PACKAGE, "rb");
 		if (pkg_old == NULL) {
 			errlog("Failed to open source package file");
 			return 1;
 		}
 		
-		pkg_new = fopen(PKG_NEW, "w");
+		pkg_new = fopen(PKG_NEW, "wb");
 		if (pkg_new == NULL) {
 			errlog("Failed to create destination package file");
 			fclose(pkg_old);