diff --git a/curl-sys/Cargo.toml b/curl-sys/Cargo.toml
index 88f2a3b3a..79e0f3b69 100644
--- a/curl-sys/Cargo.toml
+++ b/curl-sys/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "curl-sys"
-version = "0.4.67+curl-8.3.0"
+version = "0.4.68+curl-8.4.0"
 authors = ["Alex Crichton <alex@alexcrichton.com>"]
 links = "curl"
 build = "build.rs"
diff --git a/curl-sys/build.rs b/curl-sys/build.rs
index 6c3ae1920..74f601b36 100644
--- a/curl-sys/build.rs
+++ b/curl-sys/build.rs
@@ -100,7 +100,7 @@ fn main() {
             .replace("@LIBCURL_LIBS@", "")
             .replace("@SUPPORT_FEATURES@", "")
             .replace("@SUPPORT_PROTOCOLS@", "")
-            .replace("@CURLVERSION@", "8.3.0"),
+            .replace("@CURLVERSION@", "8.4.0"),
     )
     .unwrap();
 
diff --git a/curl-sys/curl b/curl-sys/curl
index 6fa1d817e..d755a5f7c 160000
--- a/curl-sys/curl
+++ b/curl-sys/curl
@@ -1 +1 @@
-Subproject commit 6fa1d817e5b1a00d7d0c8168091877476b499317
+Subproject commit d755a5f7c009dd63a61b2c745180d8ba937cbfeb
diff --git a/tests/multi.rs b/tests/multi.rs
index 0c5e70150..c1e68f4a5 100644
--- a/tests/multi.rs
+++ b/tests/multi.rs
@@ -140,7 +140,6 @@ fn upload_lots() {
 
     let e = t!(m.add(h));
 
-    assert!(t!(m.perform()) > 0);
     let mut next_token = 1;
     let mut token_map = HashMap::new();
     let mut cur_timeout = None;
diff --git a/tests/post.rs b/tests/post.rs
index 15e2df7d3..3e2db5cdd 100644
--- a/tests/post.rs
+++ b/tests/post.rs
@@ -1,3 +1,4 @@
+use curl::Version;
 use std::time::Duration;
 
 macro_rules! t {
@@ -23,15 +24,26 @@ fn handle() -> Easy {
     e
 }
 
+fn multipart_boundary_size() -> usize {
+    // Versions before 8.4.0 used a smaller multipart mime boundary, so the
+    // exact content-length will differ between versions.
+    if Version::get().version_num() >= 0x80400 {
+        148
+    } else {
+        136
+    }
+}
+
 #[test]
 fn custom() {
+    multipart_boundary_size();
     let s = Server::new();
-    s.receive(
+    s.receive(&format!(
         "\
          POST / HTTP/1.1\r\n\
          Host: 127.0.0.1:$PORT\r\n\
          Accept: */*\r\n\
-         Content-Length: 142\r\n\
+         Content-Length: {}\r\n\
          Content-Type: multipart/form-data; boundary=--[..]\r\n\
          \r\n\
          --[..]\r\n\
@@ -39,7 +51,8 @@ fn custom() {
          \r\n\
          1234\r\n\
          --[..]\r\n",
-    );
+        multipart_boundary_size() + 6
+    ));
     s.send("HTTP/1.1 200 OK\r\n\r\n");
 
     let mut handle = handle();
@@ -50,15 +63,16 @@ fn custom() {
     t!(handle.perform());
 }
 
+#[cfg(feature = "static-curl")]
 #[test]
 fn buffer() {
     let s = Server::new();
-    s.receive(
+    s.receive(&format!(
         "\
          POST / HTTP/1.1\r\n\
          Host: 127.0.0.1:$PORT\r\n\
          Accept: */*\r\n\
-         Content-Length: 181\r\n\
+         Content-Length: {}\r\n\
          Content-Type: multipart/form-data; boundary=--[..]\r\n\
          \r\n\
          --[..]\r\n\
@@ -67,7 +81,8 @@ fn buffer() {
          \r\n\
          1234\r\n\
          --[..]\r\n",
-    );
+        multipart_boundary_size() + 45
+    ));
     s.send("HTTP/1.1 200 OK\r\n\r\n");
 
     let mut handle = handle();
@@ -82,6 +97,7 @@ fn buffer() {
     t!(handle.perform());
 }
 
+#[cfg(feature = "static-curl")]
 #[test]
 fn file() {
     let s = Server::new();
@@ -102,7 +118,7 @@ fn file() {
              {}\
              \r\n\
              --[..]\r\n",
-            199 + formdata.len(),
+            multipart_boundary_size() + 63 + formdata.len(),
             formdata
         )
         .as_str(),