diff --git a/configure.ac b/configure.ac
index f7d18f807..30b882100 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1234,6 +1234,16 @@ if test "$ac_cv_func_sigsetjmp" != "yes"; then
                )
 fi
 
+AC_CHECK_DECL(basename, ,
+              AC_DEFINE(NEED_BASENAME_PROTO, 1, [If you lack a fine basename() prototype]),
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+#ifdef HAVE_LIBGEN_H
+#include <libgen.h>
+#endif
+)
+
 dnl poll() might be badly emulated, as in Mac OS X 10.3 (and other BSDs?) and
 dnl to find out we make an extra check here!
 if test "$ac_cv_func_poll" = "yes"; then
diff --git a/lib/formdata.c b/lib/formdata.c
index d7c741938..171113485 100644
--- a/lib/formdata.c
+++ b/lib/formdata.c
@@ -126,6 +126,11 @@ Content-Disposition: form-data; name="FILECONTENT"
 /* The last #include file should be: */
 #include "memdebug.h"
 
+#if defined(HAVE_BASENAME) && defined(NEED_BASENAME_PROTO)
+/* This system has a basename() but no prototype for it! */
+char *basename(char *path);
+#endif
+
 /* What kind of Content-Type to use on un-specified files with unrecognized
    extensions. */
 #define HTTPPOST_CONTENTTYPE_DEFAULT "application/octet-stream"