diff --git a/compat_readpassphrase.c b/compat_readpassphrase.c
index 353868a..3bb2045 100644
--- a/compat_readpassphrase.c
+++ b/compat_readpassphrase.c
@@ -32,6 +32,18 @@
 #include <termios.h>
 #include <unistd.h>
 
+/*
+ * Macros and function required for readpassphrase(3).
+ */
+#define RPP_ECHO_OFF 0x00
+#define RPP_ECHO_ON 0x01
+#define RPP_REQUIRE_TTY 0x02
+#define RPP_FORCELOWER 0x04
+#define RPP_FORCEUPPER 0x08
+#define RPP_SEVENBIT 0x10
+#define RPP_STDIN 0x20
+char *readpassphrase(const char *, char *, size_t, int);
+
 #if !defined(_NSIG) && defined(NSIG)
 # define _NSIG NSIG
 #endif