diff --git a/openssl-sys/src/bio.rs b/openssl-sys/src/bio.rs
index c1dc9356f..f6ec71d3b 100644
--- a/openssl-sys/src/bio.rs
+++ b/openssl-sys/src/bio.rs
@@ -89,7 +89,7 @@ cfg_if! {
             BIO_ctrl(bio, BIO_CTRL_DGRAM_GET_NO_TRUNC, 0, ptr::null_mut()) as c_int
         }
         pub unsafe fn BIO_dgram_set_no_trunc(bio: *mut BIO, enable: c_int) -> c_int {
-            BIO_ctrl(bio, BIO_CTRL_DGRAM_SET_NO_TRUNC, enable, ptr::null_mut()) as c_int
+            BIO_ctrl(bio, BIO_CTRL_DGRAM_SET_NO_TRUNC, enable as c_long, ptr::null_mut()) as c_int
         }
         pub unsafe fn BIO_dgram_get_cap(bio: *mut BIO) -> u32 {
             BIO_ctrl(bio, BIO_CTRL_DGRAM_GET_CAPS, 0, ptr::null_mut()) as u32
diff --git a/openssl-sys/src/err.rs b/openssl-sys/src/err.rs
index 4a6a2775e..a2c0f0fb9 100644
--- a/openssl-sys/src/err.rs
+++ b/openssl-sys/src/err.rs
@@ -9,8 +9,8 @@ pub const ERR_LIB_ASN1: c_int = 13;
 
 cfg_if! {
     if #[cfg(ossl300)] {
-        pub const ERR_SYSTEM_FLAG: c_ulong = c_int::max_value() as c_ulong + 1;
-        pub const ERR_SYSTEM_MASK: c_ulong = c_int::max_value() as c_ulong;
+        pub const ERR_SYSTEM_FLAG: c_ulong = c_int::MAX as c_ulong + 1;
+        pub const ERR_SYSTEM_MASK: c_ulong = c_int::MAX as c_ulong;
 
         pub const ERR_LIB_OFFSET: c_ulong = 23;
         pub const ERR_LIB_MASK: c_ulong = 0xff;
diff --git a/openssl-sys/src/tls1.rs b/openssl-sys/src/tls1.rs
index 2cb08a91f..7ff0b9df9 100644
--- a/openssl-sys/src/tls1.rs
+++ b/openssl-sys/src/tls1.rs
@@ -74,7 +74,16 @@ pub unsafe fn SSL_CTX_set_tlsext_servername_callback__fixed_rust(
     ctx: *mut SSL_CTX,
     cb: Option<unsafe extern "C" fn(*mut SSL, *mut c_int, *mut c_void) -> c_int>,
 ) -> c_long {
-    SSL_CTX_callback_ctrl__fixed_rust(ctx, SSL_CTRL_SET_TLSEXT_SERVERNAME_CB, mem::transmute(cb))
+    SSL_CTX_callback_ctrl__fixed_rust(
+        ctx,
+        SSL_CTRL_SET_TLSEXT_SERVERNAME_CB,
+        mem::transmute::<
+            std::option::Option<
+                unsafe extern "C" fn(*mut SSL, *mut c_int, *mut libc::c_void) -> i32,
+            >,
+            std::option::Option<unsafe extern "C" fn()>,
+        >(cb),
+    )
 }
 
 pub const SSL_TLSEXT_ERR_OK: c_int = 0;
@@ -90,7 +99,14 @@ pub unsafe fn SSL_CTX_set_tlsext_status_cb(
     ctx: *mut SSL_CTX,
     cb: Option<unsafe extern "C" fn(*mut SSL, *mut c_void) -> c_int>,
 ) -> c_long {
-    SSL_CTX_callback_ctrl__fixed_rust(ctx, SSL_CTRL_SET_TLSEXT_STATUS_REQ_CB, mem::transmute(cb))
+    SSL_CTX_callback_ctrl__fixed_rust(
+        ctx,
+        SSL_CTRL_SET_TLSEXT_STATUS_REQ_CB,
+        mem::transmute::<
+            std::option::Option<unsafe extern "C" fn(*mut SSL, *mut c_void) -> i32>,
+            std::option::Option<unsafe extern "C" fn()>,
+        >(cb),
+    )
 }
 
 pub unsafe fn SSL_CTX_set_tlsext_status_arg(ctx: *mut SSL_CTX, arg: *mut c_void) -> c_long {