diff --git a/fipy/terms/unaryTerm.py b/fipy/terms/unaryTerm.py
index e0434c50a5..b5013f98e5 100644
--- a/fipy/terms/unaryTerm.py
+++ b/fipy/terms/unaryTerm.py
@@ -106,7 +106,7 @@ def _getDefaultSolver(self, var, solver, *args, **kwargs):
 
     def _checkVar(self, var):
         if ((var is not None)
-            and issubclass(var.dtype.type, numerix.floating)):
+            and not issubclass(var.dtype.type, numerix.floating)):
             import warnings
             warnings.warn("""sweep() or solve() are likely to produce erroneous results when `var` does not contain floats.""",
                           UserWarning, stacklevel=4)