diff --git a/bobber/lib/analysis/common.py b/bobber/lib/analysis/common.py
index b1af96c..476221a 100644
--- a/bobber/lib/analysis/common.py
+++ b/bobber/lib/analysis/common.py
@@ -244,7 +244,7 @@ def fio_command_details(log_contents: str, old_reads: dict,
     """
     commands = re.findall(r'/usr/bin/fio --rw.*', log_contents)
     if len(commands) < 2:
-        raise ValueError(f'FIO command not found in {log} file!')
+        raise ValueError('FIO command not found in the log file!')
 
     for command in commands:
         if '--rw=read' in command:
diff --git a/tests/test_fio_command_nameerror.py b/tests/test_fio_command_nameerror.py
new file mode 100644
index 0000000..90b9809
--- /dev/null
+++ b/tests/test_fio_command_nameerror.py
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: MIT
+"""Regression test for the FIO command NameError bug.
+
+When a FIO log does not contain at least two ``/usr/bin/fio --rw...``
+command lines, ``fio_command_details()`` must raise a clear ``ValueError``.
+Before the fix, the error message referenced an undefined variable ``log``,
+so callers instead got ``NameError: name 'log' is not defined``.
+"""
+import os
+import sys
+
+import pytest
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from bobber.lib.analysis.common import fio_command_details  # noqa: E402
+
+
+def test_missing_fio_commands_raises_valueerror_not_nameerror():
+    with pytest.raises(ValueError, match='FIO command not found'):
+        fio_command_details('no fio commands here', {}, {})
+
+
+def test_valid_fio_log_still_parses():
+    log_contents = (
+        '/usr/bin/fio --rw=read --bs=1M --size=1G --name=read_test\n'
+        'some output\n'
+        '/usr/bin/fio --rw=write --bs=1M --size=1G --name=write_test\n'
+    )
+    reads, writes = fio_command_details(log_contents, {}, {})
+    assert reads['rw'] == 'read'
+    assert writes['rw'] == 'write'