diff --git a/tests/toml_cli/test_init.py b/tests/toml_cli/test_init.py
index fb5feeb..ef27309 100644
--- a/tests/toml_cli/test_init.py
+++ b/tests/toml_cli/test_init.py
@@ -68,6 +68,9 @@ def test_set_value(tmp_path: pathlib.Path):
 """
     )
 
+    result = runner.invoke(app, ["set", "--toml-path", str(test_toml_path), "person.KEY_THAT_DOES_NOT_EXIST.name", "15"])
+    assert result.exit_code == 1
+
     result = runner.invoke(app, ["set", "--toml-path", str(test_toml_path), "person.age", "15"])
     assert result.exit_code == 0
     assert 'age = "15"' in test_toml_path.read_text()
diff --git a/toml_cli/__init__.py b/toml_cli/__init__.py
index aa51b14..ee286a3 100644
--- a/toml_cli/__init__.py
+++ b/toml_cli/__init__.py
@@ -51,7 +51,8 @@ def set_(
         try:
             toml_part = toml_part[key_part]
         except tomlkit.exceptions.NonExistentKey:
-            typer.echo(f"Key {key} can not set", err=True)
+            typer.echo(f"error: non-existent key '{key}' can not be set to value '{value}'", err=True)
+            exit(1)
 
     if to_int:
         value = int(value)