diff --git a/src/dc_imex.rs b/src/dc_imex.rs
index 50aa9780f..d9d785ba5 100644
--- a/src/dc_imex.rs
+++ b/src/dc_imex.rs
@@ -208,12 +208,8 @@ pub fn dc_render_setup_file(context: &Context, passphrase: &str) -> Result<Strin
         _ => Some(("Autocrypt-Prefer-Encrypt", "mutual")),
     };
     let private_key_asc = private_key.to_asc(ac_headers);
-    let encr = {
-        let private_key_asc_c = CString::yolo(private_key_asc);
-        let passphrase_c = CString::yolo(passphrase);
-        dc_pgp_symm_encrypt(passphrase_c.as_ptr(), private_key_asc_c.as_bytes())
-            .ok_or(format_err!("Failed to encrypt private key."))?
-    };
+    let encr = dc_pgp_symm_encrypt(&passphrase, private_key_asc.as_bytes())
+        .ok_or(format_err!("Failed to encrypt private key."))?;
     let replacement = format!(
         concat!(
             "-----BEGIN PGP MESSAGE-----\r\n",
@@ -445,7 +441,7 @@ pub unsafe fn dc_decrypt_setup_file(
         {
             /* decrypt symmetrically */
             if let Some(plain) = dc_pgp_symm_decrypt(
-                passphrase,
+                as_str(passphrase),
                 std::slice::from_raw_parts(binary as *const u8, binary_bytes),
             ) {
                 let payload_c = CString::new(plain).unwrap();
diff --git a/src/pgp.rs b/src/pgp.rs
index 46d1fc8b0..5adf95c51 100644
--- a/src/pgp.rs
+++ b/src/pgp.rs
@@ -1,6 +1,5 @@
 use std::collections::HashSet;
 use std::convert::TryInto;
-use std::ffi::CStr;
 use std::io::Cursor;
 use std::ptr;
 
@@ -274,32 +273,25 @@ pub fn dc_pgp_pk_decrypt(
 }
 
 /// Symmetric encryption.
-pub fn dc_pgp_symm_encrypt(passphrase: *const libc::c_char, plain: &[u8]) -> Option<String> {
-    assert!(!passphrase.is_null(), "invalid passphrase");
-
-    let pw = unsafe { CStr::from_ptr(passphrase).to_str().unwrap() };
-
+pub fn dc_pgp_symm_encrypt(passphrase: &str, plain: &[u8]) -> Option<String> {
     let mut rng = thread_rng();
     let lit_msg = Message::new_literal_bytes("", plain);
 
     let s2k = StringToKey::new_default(&mut rng);
-    let msg = lit_msg.encrypt_with_password(&mut rng, s2k, Default::default(), || pw.into());
+    let msg =
+        lit_msg.encrypt_with_password(&mut rng, s2k, Default::default(), || passphrase.into());
 
     msg.and_then(|msg| msg.to_armored_string(None)).ok()
 }
 
 /// Symmetric decryption.
-pub fn dc_pgp_symm_decrypt(passphrase: *const libc::c_char, ctext: &[u8]) -> Option<Vec<u8>> {
-    assert!(!passphrase.is_null(), "invalid passphrase");
-
-    let pw = unsafe { CStr::from_ptr(passphrase).to_str().unwrap() };
-
+pub fn dc_pgp_symm_decrypt(passphrase: &str, ctext: &[u8]) -> Option<Vec<u8>> {
     let enc_msg = Message::from_bytes(Cursor::new(ctext));
 
     enc_msg
         .and_then(|msg| {
             let mut decryptor = msg
-                .decrypt_with_password(|| pw.into())
+                .decrypt_with_password(|| passphrase.into())
                 .expect("failed decryption");
             decryptor.next().expect("no message")
         })