diff --git a/src/commands.rs b/src/commands.rs
index 7a00077e0..200d4da00 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -3484,6 +3484,14 @@ fn cmd_new(ui: &mut Ui, command: &CommandHelper, args: &NewArgs) -> Result<(), C
     );
     for revision_arg in &args.revisions {
         let commit = workspace_command.resolve_single_rev(revision_arg)?;
+        if let Some(i) = commits.iter().position(|c| c == &commit) {
+            return Err(CommandError::UserError(format!(
+                r#"Revset "{}" and "{}" resolved to the same revision {}"#,
+                args.revisions[i],
+                revision_arg,
+                short_commit_hash(commit.id()),
+            )));
+        }
         parent_ids.push(commit.id().clone());
         commits.push(commit);
     }
diff --git a/tests/test_new_command.rs b/tests/test_new_command.rs
index 56c4b6b1a..9e680e7ad 100644
--- a/tests/test_new_command.rs
+++ b/tests/test_new_command.rs
@@ -86,6 +86,12 @@ fn test_new_merge() {
     // `jj merge` with less than two arguments is an error
     test_env.jj_cmd_cli_error(&repo_path, &["merge"]);
     test_env.jj_cmd_cli_error(&repo_path, &["merge", "main"]);
+
+    // merge with non-unique revisions
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["new", "@", "c34d"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Revset "@" and "c34d" resolved to the same revision c34d60aa3322
+    "###);
 }
 
 fn get_log_output(test_env: &TestEnvironment, repo_path: &Path) -> String {