diff --git a/ext/fileinfo/libmagic/apprentice.c b/ext/fileinfo/libmagic/apprentice.c
index fd82564bff7..b137405da22 100644
--- a/ext/fileinfo/libmagic/apprentice.c
+++ b/ext/fileinfo/libmagic/apprentice.c
@@ -1269,7 +1269,7 @@ file_signextend(struct magic_set *ms, struct magic *m, uint64_t v)
 		 * the sign extension must have happened.
 		 */
 		case FILE_BYTE:
-			v = (char) v;
+			v = (signed char) v;
 			break;
 		case FILE_SHORT:
 		case FILE_BESHORT: