diff --git a/backend/tests/test_library.c b/backend/tests/test_library.c
index db164a08..7a4fe08e 100644
--- a/backend/tests/test_library.c
+++ b/backend/tests/test_library.c
@@ -683,7 +683,7 @@ static void test_escape_char_process_test(const testCtx *const p_ctx) {
 
         symbol.symbology = data[i].symbology;
         symbol.input_mode = data[i].input_mode;
-        length = strlen(data[i].data);
+        length = (int) strlen(data[i].data);
 
         escaped_len = length;
         ret = escape_char_process_test(&symbol, (unsigned char *) data[i].data, &escaped_len, NULL);
diff --git a/getopt/getopt.c b/getopt/getopt.c
index 30199e9c..f3f1e441 100644
--- a/getopt/getopt.c
+++ b/getopt/getopt.c
@@ -197,7 +197,8 @@ static char *posixly_correct;
    whose names are inconsistent.  */
 
 #ifndef getenv
-extern char *getenv ();
+/* zint: prototype it to avoid warning `-Wdeprecated-non-prototype` (will be error in C2x) */
+extern char *getenv (const char *); /* was extern char *getenv (); */
 #endif
 
 #endif /* not __GNU_LIBRARY__ */
diff --git a/getopt/getopt.h b/getopt/getopt.h
index cc45f46f..2a2c54ee 100644
--- a/getopt/getopt.h
+++ b/getopt/getopt.h
@@ -135,7 +135,8 @@ struct option
    arguments to the option '\0'.  This behavior is specific to the GNU
    `getopt'.  */
 
-#ifdef __GNU_LIBRARY__
+/* zint: prototype it always to avoid warning `-Wdeprecated-non-prototype` (will be error in C2x) */
+#ifdef 1 /* was __GNU_LIBRARY__ */
 /* Many other libraries have conflicting prototypes for getopt, with
    differences in the consts, in stdlib.h.  To avoid compilation
    errors, only prototype getopt for the GNU C library.  */