diff --git a/pysnooper/pysnooper.py b/pysnooper/pysnooper.py
index 8d0c6a7..19139d3 100644
--- a/pysnooper/pysnooper.py
+++ b/pysnooper/pysnooper.py
@@ -23,7 +23,7 @@ def get_write_function(output):
             stderr.write(s)
     elif isinstance(output, (pycompat.PathLike, str)):
         def write(s):
-            with open(output_path, 'a') as output_file:
+            with open(output, 'a') as output_file:
                 output_file.write(s)
     else:
         assert isinstance(output, utils.WritableStream)
diff --git a/tests/test_pysnooper.py b/tests/test_pysnooper.py
index 13f0401..27af77d 100644
--- a/tests/test_pysnooper.py
+++ b/tests/test_pysnooper.py
@@ -7,6 +7,7 @@ import abc
 
 from python_toolbox import caching
 from python_toolbox import sys_tools
+from python_toolbox import temp_file_tools
 
 import pysnooper
 
@@ -169,3 +170,30 @@ def test_method_and_prefix():
         ),
         prefix='ZZZ'
     )
+
+def test_file_output():
+
+    with temp_file_tools.create_temp_folder(prefix='pysnooper') as folder:
+        path = folder / 'foo.log'
+        @pysnooper.snoop(str(path))
+        def my_function(foo):
+            x = 7
+            y = 8
+            return y + x
+        result = my_function('baba')
+        assert result == 15
+        output = path.open().read()
+        assert_output(
+            output,
+            (
+                VariableEntry('foo', value_regex="u?'baba'"),
+                CallEntry(),
+                LineEntry('x = 7'),
+                VariableEntry('x', '7'),
+                LineEntry('y = 8'),
+                VariableEntry('y', '8'),
+                LineEntry('return y + x'),
+                ReturnEntry('return y + x'),
+            )
+        )
+