diff --git a/lib/des/rsa.c b/lib/des/rsa.c
index 2f98128b6..9b723263d 100644
--- a/lib/des/rsa.c
+++ b/lib/des/rsa.c
@@ -351,7 +351,7 @@ d2i_RSAPrivateKey(RSA *rsa, const unsigned char **pp, size_t len)
 }
 
 int
-i2d_RSAPublicKey(RSA *rsa, const unsigned char **pp)
+i2d_RSAPublicKey(RSA *rsa, unsigned char **pp)
 {
     RSAPublicKey data;
     size_t size;
diff --git a/lib/des/rsa.h b/lib/des/rsa.h
index 2fa1db3e5..98c320153 100644
--- a/lib/des/rsa.h
+++ b/lib/des/rsa.h
@@ -161,6 +161,6 @@ int RSA_verify(int, const unsigned char *, unsigned int,
 	       unsigned char *, unsigned int, RSA *);
 
 RSA *	d2i_RSAPrivateKey(RSA *, const unsigned char **, size_t);
-int	i2d_RSAPublicKey(RSA *, const unsigned char **);
+int	i2d_RSAPublicKey(RSA *, unsigned char **);
 
 #endif /* _HEIM_RSA_H */