diff --git a/src/uu/truncate/src/truncate.rs b/src/uu/truncate/src/truncate.rs
index 997916b24a8..4461a4db280 100644
--- a/src/uu/truncate/src/truncate.rs
+++ b/src/uu/truncate/src/truncate.rs
@@ -363,5 +363,31 @@ mod tests {
         assert_eq!(TruncateMode::RoundUp(8).to_size(10), Some(16));
         assert_eq!(TruncateMode::RoundUp(8).to_size(16), Some(16));
         assert_eq!(TruncateMode::RoundDown(0).to_size(123), None);
+        assert_eq!(TruncateMode::RoundUp(0).to_size(123), None);
+    }
+
+    #[test]
+    fn test_round_up_when_file_smaller_than_size() {
+        // fsize < size: must round up to size itself
+        assert_eq!(
+            TruncateMode::RoundUp(131_072).to_size(24_696),
+            Some(131_072)
+        );
+        assert_eq!(TruncateMode::RoundUp(4096).to_size(1), Some(4096));
+        assert_eq!(TruncateMode::RoundUp(100).to_size(50), Some(100));
+    }
+
+    #[test]
+    fn test_round_up_already_aligned() {
+        assert_eq!(TruncateMode::RoundUp(4096).to_size(0), Some(0));
+        assert_eq!(TruncateMode::RoundUp(4096).to_size(4096), Some(4096));
+        assert_eq!(TruncateMode::RoundUp(4096).to_size(8192), Some(8192));
+    }
+
+    #[test]
+    fn test_round_up_not_aligned() {
+        // fsize > size but not a multiple: must round up to next multiple
+        assert_eq!(TruncateMode::RoundUp(4096).to_size(5000), Some(8192));
+        assert_eq!(TruncateMode::RoundUp(8).to_size(13), Some(16));
     }
 }
diff --git a/tests/by-util/test_truncate.rs b/tests/by-util/test_truncate.rs
index 63c4442bd55..3057dcfbe68 100644
--- a/tests/by-util/test_truncate.rs
+++ b/tests/by-util/test_truncate.rs
@@ -173,6 +173,42 @@ fn test_round_up() {
     assert_eq!(expected, actual, "expected '{expected}' got '{actual}'");
 }
 
+#[test]
+fn test_round_up_file_smaller_than_size() {
+    let expected = 4096;
+    let (at, mut ucmd) = at_and_ucmd!();
+    let mut file = at.make_file(FILE2);
+    file.write_all(b"1234567890").unwrap();
+    ucmd.args(&["--size", "%4K", FILE2]).succeeds();
+    file.seek(SeekFrom::End(0)).unwrap();
+    let actual = file.stream_position().unwrap();
+    assert_eq!(expected, actual);
+}
+
+#[test]
+fn test_round_up_unaligned() {
+    let expected = 16;
+    let (at, mut ucmd) = at_and_ucmd!();
+    let mut file = at.make_file(FILE2);
+    file.write_all(b"1234567890123").unwrap();
+    ucmd.args(&["--size", "%8", FILE2]).succeeds();
+    file.seek(SeekFrom::End(0)).unwrap();
+    let actual = file.stream_position().unwrap();
+    assert_eq!(expected, actual);
+}
+
+#[test]
+fn test_round_up_already_aligned() {
+    let expected = 8;
+    let (at, mut ucmd) = at_and_ucmd!();
+    let mut file = at.make_file(FILE2);
+    file.write_all(b"12345678").unwrap();
+    ucmd.args(&["--size", "%4", FILE2]).succeeds();
+    file.seek(SeekFrom::End(0)).unwrap();
+    let actual = file.stream_position().unwrap();
+    assert_eq!(expected, actual);
+}
+
 #[test]
 fn test_size_and_reference() {
     let expected = 15;