diff --git a/src/console/mod.rs b/src/console/mod.rs
index 42d22f97..df7a842f 100644
--- a/src/console/mod.rs
+++ b/src/console/mod.rs
@@ -91,7 +91,7 @@ impl Log for ConsoleLogger {
         let _ = write_fmt(format_args!(
             "[{:5}.{:06}] {}: {}\r\n",
             uptime.as_secs(),
-            uptime.as_micros(),
+            uptime.subsec_micros(),
             record
                 .module_path()
                 .map(|x| x.strip_prefix("moss::").unwrap_or(x))
diff --git a/src/fs/reg.rs b/src/fs/reg.rs
index 71860af7..bc9ed141 100644
--- a/src/fs/reg.rs
+++ b/src/fs/reg.rs
@@ -12,7 +12,7 @@ use async_trait::async_trait;
 use core::{cmp::min, pin::Pin};
 use libkernel::{
     error::Result,
-    fs::{Inode, SeekFrom},
+    fs::{Inode, OpenFlags, SeekFrom},
     memory::{PAGE_SIZE, address::UA},
 };
 
@@ -63,6 +63,17 @@ impl FileOps for RegFile {
         Ok(total_bytes_read)
     }
 
+    /// Writes at the cursor, or at the end of the file if it was opened with
+    /// `O_APPEND`, and advances the cursor past the data written.
+    async fn write(&mut self, ctx: &mut FileCtx, buf: UA, count: usize) -> Result<usize> {
+        if ctx.flags.contains(OpenFlags::O_APPEND) {
+            ctx.pos = self.inode.getattr().await?.size;
+        }
+        let bytes_written = self.writeat(buf, count, ctx.pos).await?;
+        ctx.pos += bytes_written as u64;
+        Ok(bytes_written)
+    }
+
     /// Writes data from `buf` to the current file position.
     /// The file's cursor is advanced by the number of bytes written.
     async fn writeat(&mut self, mut buf: UA, mut count: usize, mut offset: u64) -> Result<usize> {
diff --git a/src/fs/syscalls/chdir.rs b/src/fs/syscalls/chdir.rs
index b116da5a..71bc3968 100644
--- a/src/fs/syscalls/chdir.rs
+++ b/src/fs/syscalls/chdir.rs
@@ -20,7 +20,7 @@ pub async fn sys_getcwd(ctx: &ProcessCtx, buf: UA, len: usize) -> Result<usize>
     let slice = cstr.as_bytes_with_nul();
 
     if slice.len() > len {
-        return Err(KernelError::TooLarge);
+        return Err(KernelError::RangeError);
     }
 
     copy_to_user_slice(slice, buf).await?;
diff --git a/usertest/src/fs.rs b/usertest/src/fs.rs
index a3f62543..38969d42 100644
--- a/usertest/src/fs.rs
+++ b/usertest/src/fs.rs
@@ -612,3 +612,30 @@ fn test_rust_dir() {
 }
 
 register_test!(test_rust_dir);
+
+fn test_o_append() {
+    use std::io::{Seek, SeekFrom, Write};
+    let path = "/tmp/o_append_test";
+    fs::write(path, "first\n").unwrap();
+    let mut file = fs::OpenOptions::new().append(true).open(path).unwrap();
+    file.write_all(b"second\n").unwrap();
+    // O_APPEND writes always go to the end, even after seeking elsewhere.
+    file.seek(SeekFrom::Start(0)).unwrap();
+    file.write_all(b"third\n").unwrap();
+    assert_eq!(fs::read_to_string(path).unwrap(), "first\nsecond\nthird\n");
+    fs::remove_file(path).unwrap();
+}
+
+register_test!(test_o_append);
+
+fn test_getcwd_buffer_too_small() {
+    let mut buf = [0 as libc::c_char; 1];
+    let ret = unsafe { libc::getcwd(buf.as_mut_ptr(), buf.len()) };
+    assert!(ret.is_null());
+    assert_eq!(
+        std::io::Error::last_os_error().raw_os_error(),
+        Some(libc::ERANGE)
+    );
+}
+
+register_test!(test_getcwd_buffer_too_small);