diff --git a/src/uu/cksum/src/cksum.rs b/src/uu/cksum/src/cksum.rs
index 9f6ed3bec..1b6ace6da 100644
--- a/src/uu/cksum/src/cksum.rs
+++ b/src/uu/cksum/src/cksum.rs
@@ -376,7 +376,13 @@ fn calculate_length(algo_name: &str, length: usize) -> UResult<Option<usize>> {
         n => {
             if algo_name == ALGORITHM_OPTIONS_BLAKE2B {
                 // Divide by 8, as our blake2b implementation expects bytes instead of bits.
-                Ok(Some(n / 8))
+                if n == 512 {
+                    // When length is 512, it is blake2b's default.
+                    // So, don't show it
+                    Ok(None)
+                } else {
+                    Ok(Some(n / 8))
+                }
             } else {
                 Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
diff --git a/tests/by-util/test_cksum.rs b/tests/by-util/test_cksum.rs
index 71fc1dece..62a182a7f 100644
--- a/tests/by-util/test_cksum.rs
+++ b/tests/by-util/test_cksum.rs
@@ -491,9 +491,6 @@ fn test_check_error_incorrect_format() {
 #[test]
 fn test_dev_null() {
     let scene = TestScenario::new(util_name!());
-    let at = &scene.fixtures;
-
-    at.touch("f");
 
     scene
         .ucmd()
@@ -505,6 +502,33 @@ fn test_dev_null() {
         .stdout_contains("d41d8cd98f00b204e9800998ecf8427e ");
 }
 
+#[cfg(unix)]
+#[test]
+fn test_blake2b_512() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    at.touch("f");
+
+    scene
+        .ucmd()
+        .arg("-a")
+        .arg("blake2b")
+        .arg("-l512")
+        .arg("f")
+        .succeeds()
+        .stdout_contains("BLAKE2b (f) = 786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce");
+
+    // test also the read
+    at.write("checksum", "BLAKE2b (f) = 786a02f742015903c6c6fd852552d272912f4740e15847618a86e217f71f5419d25e1031afee585313896444934eb04b903a685b1448b755d56f701afe9be2ce");
+    scene
+        .ucmd()
+        .arg("--check")
+        .arg("checksum")
+        .succeeds()
+        .stdout_contains("f: OK");
+}
+
 #[test]
 fn test_reset_binary() {
     let scene = TestScenario::new(util_name!());