Index: wflow-py/wflow/wflow_bmi.py
===================================================================
diff -u -r42d3c1c35dbb2f934cbc815646e166e2c9bfa2c1 -r8de00630f14f2ad1ede84fc18395c2b7614dc875
--- wflow-py/wflow/wflow_bmi.py	(.../wflow_bmi.py)	(revision 42d3c1c35dbb2f934cbc815646e166e2c9bfa2c1)
+++ wflow-py/wflow/wflow_bmi.py	(.../wflow_bmi.py)	(revision 8de00630f14f2ad1ede84fc18395c2b7614dc875)
@@ -92,6 +92,7 @@
         Return type string, compatible with numpy.
         Propagate the model one timestep?
         """
+        # TODO: fix dt = -1 problem, what do we want here?
         #curstep = self.dynModel.wf_
         if dt != -1:
             self.dynModel._runDynamic(self.currenttimestep, self.currenttimestep)
@@ -458,6 +459,11 @@
         """
         curtime = self.get_current_time()
 
+        if abs(time - curtime)% self.dynModel.timestepsecs != 0:
+            self.bmilogger.error('update_until: timespan not dividable by timestep: ' + str(abs(time - curtime)) +
+                                 ' and ' + str(self.dynModel.timestepsecs))
+            raise ValueError("Update in time not a multiple of timestep")
+
         if curtime > time:
             timespan = curtime - time
             nrstepsback = int(timespan/self.dynModel.timestepsecs)