diff --git a/src/caosadvancedtools/table_importer.py b/src/caosadvancedtools/table_importer.py
index 90f82e7e111ecb310ca2e463e4868bd27429c7e8..72a51c0f2d461c05079168195e389e75139c6d2d 100755
--- a/src/caosadvancedtools/table_importer.py
+++ b/src/caosadvancedtools/table_importer.py
@@ -546,6 +546,8 @@ class CSVImporter(TableImporter):
             error_dict = {}
             columns_with_errors = []
             for key, dtype in self.datatypes.items():
+                if key not in df.columns:
+                    continue
                 try:
                     df[key].astype(dtype)
                 except (TypeError, ValueError):
diff --git a/unittests/test_table_importer.py b/unittests/test_table_importer.py
index 7a330ddfe0b0b82cb6d8dc9d4b5883e5ed604ac1..768e3f0caea9fc826d46f095c5213c3f6e4ca5a0 100644
--- a/unittests/test_table_importer.py
+++ b/unittests/test_table_importer.py
@@ -398,7 +398,8 @@ class CSVImporterTest(TableImporterTest):
         kwargs = {
             "datatypes": {
                 "int": int,
-                "float": float
+                "float": float,
+                "not-in-table": str  # An unused datatype definition must not cause problems.
             },
             "obligatory_columns": ["int"],
             "converters": {}