diff --git a/openssl/Cargo.toml b/openssl/Cargo.toml
index 39f2fc65..f9288bfa 100644
--- a/openssl/Cargo.toml
+++ b/openssl/Cargo.toml
@@ -27,6 +27,7 @@ ecdh_auto = ["openssl-sys-extras/ecdh_auto"]
 pkcs5_pbkdf2_hmac = ["openssl-sys/pkcs5_pbkdf2_hmac"]
 
 nightly = []
+catch_unwind = []
 
 [dependencies]
 bitflags = ">= 0.5.0, < 0.8.0"
diff --git a/openssl/src/crypto/mod.rs b/openssl/src/crypto/mod.rs
index 9d79b8b0..481eb05c 100644
--- a/openssl/src/crypto/mod.rs
+++ b/openssl/src/crypto/mod.rs
@@ -24,6 +24,7 @@ pub mod rand;
 pub mod symm;
 pub mod memcmp;
 pub mod rsa;
+#[cfg(feature = "catch_unwind")]
 mod util;
 
 mod symm_internal;
diff --git a/openssl/src/crypto/pkey.rs b/openssl/src/crypto/pkey.rs
index 238c1b9e..bbb8427d 100644
--- a/openssl/src/crypto/pkey.rs
+++ b/openssl/src/crypto/pkey.rs
@@ -1,4 +1,4 @@
-use libc::{c_int, c_uint, c_ulong, c_void, c_char};
+use libc::{c_int, c_uint, c_ulong};
 use std::io;
 use std::io::prelude::*;
 use std::iter::repeat;
@@ -12,6 +12,10 @@ use crypto::hash::Type as HashType;
 use ffi;
 use ssl::error::{SslError, StreamError};
 use crypto::rsa::RSA;
+
+#[cfg(feature = "catch_unwind")]
+use libc::{c_void, c_char};
+#[cfg(feature = "catch_unwind")]
 use crypto::util::{CallbackState, invoke_passwd_cb};
 
 #[derive(Copy, Clone)]
@@ -99,6 +103,7 @@ impl PKey {
     ///
     /// The callback will be passed the password buffer and should return the number of characters
     /// placed into the buffer.
+    #[cfg(feature = "catch_unwind")]
     pub fn private_key_from_pem_cb<R, F>(reader: &mut R, pass_cb: F) -> Result<PKey, SslError>
         where R: Read, F: FnMut(&mut [c_char]) -> usize
     {
diff --git a/openssl/src/crypto/rsa.rs b/openssl/src/crypto/rsa.rs
index c7f5cfaf..a67fe38e 100644
--- a/openssl/src/crypto/rsa.rs
+++ b/openssl/src/crypto/rsa.rs
@@ -3,12 +3,16 @@ use std::fmt;
 use ssl::error::{SslError, StreamError};
 use std::ptr;
 use std::io::{self, Read, Write};
-use libc::{c_int, c_void, c_char};
+use libc::c_int;
 
 use bn::BigNum;
 use bio::MemBio;
 use crypto::HashTypeInternals;
 use crypto::hash;
+
+#[cfg(feature = "catch_unwind")]
+use libc::{c_void, c_char};
+#[cfg(feature = "catch_unwind")]
 use crypto::util::{CallbackState, invoke_passwd_cb};
 
 pub struct RSA(*mut ffi::RSA);
@@ -78,6 +82,7 @@ impl RSA {
     }
 
     /// Reads an RSA private key from PEM formatted data and supplies a password callback.
+    #[cfg(feature = "catch_unwind")]
     pub fn private_key_from_pem_cb<R, F>(reader: &mut R, pass_cb: F) -> Result<RSA, SslError>
         where R: Read, F: FnMut(&mut [c_char]) -> usize
     {