diff --git a/pyVlsv/vlsvreader.py b/pyVlsv/vlsvreader.py
index ed79a8d8..f310990e 100644
--- a/pyVlsv/vlsvreader.py
+++ b/pyVlsv/vlsvreader.py
@@ -1235,7 +1235,9 @@ def read_interpolated_variable(self, name, coords, operator="pass",periodic=[Tru
       
       # Check one value for the length
       test_variable = self.read_variable(name,cellids=[1],operator=operator)
-      if isinstance(test_variable, Iterable):
+      if isinstance(test_variable,np.ma.core.MaskedConstant):
+         value_length=1
+      elif isinstance(test_variable, Iterable):
          value_length=len(test_variable)
       else:
          value_length=1