diff --git a/newlib/libc/posix/ftw.c b/newlib/libc/posix/ftw.c
index 79e63582ce..ab88fd6f4c 100644
--- a/newlib/libc/posix/ftw.c
+++ b/newlib/libc/posix/ftw.c
@@ -25,12 +25,18 @@
 
 #include <ftw.h>
 
+/* Static callback pointer to maintain the ftw callback between calls */
+static int (*ftw_callback)(const char *, const struct stat *, int);
+
+static int ftw_wrapper(const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf)
+{
+	return ftw_callback(fpath, sb, typeflag);
+}
+
 int ftw(const char *path, int (*fn)(const char *, const struct stat *, int), int fd_limit)
 {
-	/* The following cast assumes that calling a function with one
-	 * argument more than it needs behaves as expected. This is
-	 * actually undefined, but works on all real-world machines. */
-	return nftw(path, (int (*)())fn, fd_limit, FTW_PHYS);
+	ftw_callback = fn;
+	return nftw(path, ftw_wrapper, fd_limit, FTW_PHYS);
 }
 
 #endif /* ! HAVE_OPENDIR */
diff --git a/newlib/libc/posix/glob.c b/newlib/libc/posix/glob.c
index 20eec0263b..7dc3cbbe11 100644
--- a/newlib/libc/posix/glob.c
+++ b/newlib/libc/posix/glob.c
@@ -620,7 +620,7 @@ glob3(pathbuf, pathend, pathend_last, pattern, restpattern, pglob, limit)
 	 * and dirent.h as taking pointers to differently typed opaque
 	 * structures.
 	 */
-	struct dirent *(*readdirfunc)();
+	struct dirent *(*readdirfunc)(void *);
 
 	if (pathend > pathend_last)
 		return (1);
@@ -645,7 +645,7 @@ glob3(pathbuf, pathend, pathend_last, pattern, restpattern, pglob, limit)
 	if (pglob->gl_flags & GLOB_ALTDIRFUNC)
 		readdirfunc = pglob->gl_readdir;
 	else
-		readdirfunc = readdir;
+		readdirfunc = (struct dirent *(*)(void *))readdir;
 	while ((dp = (*readdirfunc)(dirp))) {
 		u_char *sc;
 		Char *dc;