diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 536bf08..55fd7f0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -52,7 +52,7 @@ jobs:
         os: [ubuntu-latest, windows-latest]
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.48']
+        rust: ['1.63']
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust
diff --git a/Cargo.toml b/Cargo.toml
index 9ee6f3c..42c4b47 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,7 +6,7 @@ name = "async-fs"
 version = "1.6.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
-rust-version = "1.48"
+rust-version = "1.63"
 description = "Async filesystem primitives"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-fs"
diff --git a/build.rs b/build.rs
deleted file mode 100644
index 10a25b1..0000000
--- a/build.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-fn main() {
-    let cfg = match autocfg::AutoCfg::new() {
-        Ok(cfg) => cfg,
-        Err(e) => {
-            println!(
-                "cargo:warning=async-fs: failed to detect compiler features: {}",
-                e
-            );
-            return;
-        }
-    };
-
-    if !cfg.probe_rustc_version(1, 63) {
-        autocfg::emit("async_fs_no_io_safety");
-    }
-}
diff --git a/src/lib.rs b/src/lib.rs
index 80235ed..f0e5e53 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1091,28 +1091,28 @@ impl std::os::windows::io::AsRawHandle for File {
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), unix))]
+#[cfg(unix)]
 impl From<std::os::unix::io::OwnedFd> for File {
     fn from(fd: std::os::unix::io::OwnedFd) -> Self {
         File::from(std::fs::File::from(fd))
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), windows))]
+#[cfg(windows)]
 impl From<std::os::windows::io::OwnedHandle> for File {
     fn from(fd: std::os::windows::io::OwnedHandle) -> Self {
         File::from(std::fs::File::from(fd))
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), unix))]
+#[cfg(unix)]
 impl std::os::unix::io::AsFd for File {
     fn as_fd(&self) -> std::os::unix::io::BorrowedFd<'_> {
         self.file.as_fd()
     }
 }
 
-#[cfg(all(not(async_fs_no_io_safety), windows))]
+#[cfg(windows)]
 impl std::os::windows::io::AsHandle for File {
     fn as_handle(&self) -> std::os::windows::io::BorrowedHandle<'_> {
         self.file.as_handle()