diff --git frontend/parse.c frontend/parse.c
index 4a6b660..adf63fa 100644
--- frontend/parse.c
+++ frontend/parse.c
@@ -137,6 +137,26 @@ static iconv_t os2_iconv_open (const char *tocode, const char *fromcode)
 static int const lame_alpha_version_enabled = LAME_ALPHA_VERSION;
 static int const internal_opts_enabled = INTERNAL_OPTS;
 
+/* Mac OS X before 10.7 does not implement strnlen(), so ... */
+/* Find the length of S, but scan at most MAXLEN characters.  If no '\0'
+   terminator is found within the first MAXLEN characters, return MAXLEN. */
+#ifdef __APPLE__
+#include <AvailabilityMacros.h>
+#endif
+#if defined(__APPLE__) && \
+    (!defined(MAC_OS_X_VERSION_MIN_REQUIRED) || MAC_OS_X_VERSION_MIN_REQUIRED < 1070)
+static size_t
+strnlen(const char *s, size_t maxlen)
+{
+    const char *e;
+    size_t  n;
+
+    for (e = s, n = 0; *e && n < maxlen; e++, n++)
+        ;
+    return n;
+}
+#endif
+
 /* GLOBAL VARIABLES.  set by parse_args() */
 /* we need to clean this up */