diff --git a/pymeasure/experiment/results.py b/pymeasure/experiment/results.py
index 921306a201..c52853e7c9 100644
--- a/pymeasure/experiment/results.py
+++ b/pymeasure/experiment/results.py
@@ -121,8 +121,6 @@ def unique_filename(directory, prefix='DATA', suffix='', ext='csv',
 class CSVFormatter(logging.Formatter):
     """ Formatter of data results """
 
-    numeric_types = (float, int, Decimal)
-
     def __init__(self, columns, delimiter=','):
         """Creates a csv formatter for a given list of columns (=header).
 
@@ -146,7 +144,7 @@ def format(self, record):
         line = []
         for x in self.columns:
             value = record.get(x, float("nan"))
-            if type(value) in self.numeric_types:
+            if isinstance(value, (float, int, Decimal)) and type(value) is not bool:
                 line.append(f"{value}")
             else:
                 units = self.units.get(x, None)
diff --git a/tests/experiment/test_results.py b/tests/experiment/test_results.py
index 0d4035567c..cb09bf1364 100644
--- a/tests/experiment/test_results.py
+++ b/tests/experiment/test_results.py
@@ -70,7 +70,9 @@ def test_csv_formatter_format(self):
                               ('magnetic (T)', 7, "7"),
                               ('string', "abcdef", "abcdef"),
                               ('count', 9 * ureg.dimensionless, "9"),
-                              ('boolean', True, "True")
+                              ('boolean', True, "True"),
+                              ('numpy (V)', np.float64(1.1), "1.1"),
+                              ('boolean nan (V)', True, "nan"),
                               ))
     def test_unitful(self, head, value, result):
         """Test, whether units are appended correctly"""