diff --git a/scopesim/tests/test_utils_functions.py b/scopesim/tests/test_utils_functions.py
index 6872a7f1..adb994f2 100644
--- a/scopesim/tests/test_utils_functions.py
+++ b/scopesim/tests/test_utils_functions.py
@@ -200,6 +200,15 @@ def test_converts_astropy_table(self):
                     names=["seeds", "seeds2"])
         assert utils.from_currsys(tbl["seeds2"][1]) is None
 
+    def test_converts_string_numericals_to_floats(self):
+        old = rc.__currsys__["!SIM.sub_pixel.fraction"]
+        rc.__currsys__["!SIM.sub_pixel.fraction"] = "1e0"
+
+        result = utils.from_currsys("!SIM.sub_pixel.fraction")
+        assert isinstance(result, float)
+        assert result == 1
+
+        rc.__currsys__["!SIM.sub_pixel.flag"] = old
 
 
 # load_example_optical_train modifies __currsys__!