diff --git a/pymbolic/interop/sympy.py b/pymbolic/interop/sympy.py
index c5e1e05a821462f52d2a1044c414c72c8fae7e9a..2ccb9fe4072b83c7978572ad31f1e636824ed0e3 100644
--- a/pymbolic/interop/sympy.py
+++ b/pymbolic/interop/sympy.py
@@ -125,7 +125,7 @@ class PymbolicToSympyMapper(PymbolicToSympyLikeMapper):
         elif expr.operator == ">=":
             return self.sym.GreaterThan(left, right)
         else:
-            raise NotImplementedError("Cannot understand operator {}".format(expr.operator))
+            raise NotImplementedError("Unknown operator '%s'" % expr.operator)
 
 # }}}
 
diff --git a/test/test_sympy.py b/test/test_sympy.py
index e5a00a883cbb3c1e041d3f938d334186b49f0dc5..e0429bb3eaf327725a1846b3450f4a41391530c7 100644
--- a/test/test_sympy.py
+++ b/test/test_sympy.py
@@ -115,6 +115,7 @@ def test_pymbolic_to_sympy():
 
 
 def test_sympy_if_condition():
+    pytest.importorskip("sympy")
     from pymbolic.interop.sympy import PymbolicToSympyMapper, SympyToPymbolicMapper
     forward = PymbolicToSympyMapper()
     backward = SympyToPymbolicMapper()