diff --git a/openssl-sys/src/lib.rs b/openssl-sys/src/lib.rs
index 6fe44750..67b93f25 100644
--- a/openssl-sys/src/lib.rs
+++ b/openssl-sys/src/lib.rs
@@ -344,6 +344,9 @@ extern {
     pub fn BIO_new_socket(sock: c_int, close_flag: c_int) -> *mut BIO;
     pub fn BIO_read(b: *mut BIO, buf: *mut c_void, len: c_int) -> c_int;
     pub fn BIO_write(b: *mut BIO, buf: *const c_void, len: c_int) -> c_int;
+    #[cfg(ossl101)]
+    pub fn BIO_new_mem_buf(buf: *mut c_void, len: c_int) -> *mut BIO;
+    #[cfg(not(ossl101))]
     pub fn BIO_new_mem_buf(buf: *const c_void, len: c_int) -> *mut BIO;
     pub fn BIO_set_flags(b: *mut BIO, flags: c_int);
     pub fn BIO_clear_flags(b: *mut BIO, flags: c_int);
diff --git a/openssl/src/bio.rs b/openssl/src/bio.rs
index 0d82a6c3..22d2cee3 100644
--- a/openssl/src/bio.rs
+++ b/openssl/src/bio.rs
@@ -22,7 +22,7 @@ impl<'a> MemBioSlice<'a> {
 
         assert!(buf.len() <= c_int::max_value() as usize);
         let bio = unsafe {
-            try_ssl_null!(ffi::BIO_new_mem_buf(buf.as_ptr() as *const _, buf.len() as c_int))
+            try_ssl_null!(BIO_new_mem_buf(buf.as_ptr() as *const _, buf.len() as c_int))
         };
 
         Ok(MemBioSlice(bio, PhantomData))
@@ -65,3 +65,12 @@ impl MemBio {
         }
     }
 }
+
+#[cfg(not(ossl101))]
+use ffi::BIO_new_mem_buf;
+
+#[cfg(ossl101)]
+#[allow(bad_style)]
+unsafe fn BIO_new_mem_buf(buf: *const ::libc::c_void, len: ::libc::c_int) -> *mut ffi::BIO {
+    ffi::BIO_new_mem_buf(buf as *mut _, len)
+}
diff --git a/systest/build.rs b/systest/build.rs
index 94c5534e..8fac5536 100644
--- a/systest/build.rs
+++ b/systest/build.rs
@@ -81,10 +81,6 @@ fn main() {
             s == "X509V3_EXT_conf_nid" ||       // weird lhash first param
             s == "X509V3_EXT_conf" ||           // weird lhash first param
 
-            // one parameter is `const` in OpenSSL 1.0.1, no need for a new
-            // definition or a new file here.
-            (s == "BIO_new_mem_buf" && env::var("DEP_OPENSSL_IS_101").is_ok()) ||
-
         // Skip some functions with function pointers on windows, not entirely
         // sure how to get them to work out...
         (target.contains("windows") && {