diff --git a/FDTD/engine.cpp b/FDTD/engine.cpp
index 277234f..5b25ba2 100644
--- a/FDTD/engine.cpp
+++ b/FDTD/engine.cpp
@@ -82,7 +82,7 @@ bool Engine::IterateTS(unsigned int iterTS)
 		for (unsigned int n=0;n<Op->E_Exc_Count;++n)
 		{
 			exc_pos = (int)numTS - (int)Op->E_Exc_delay[n];
-			exc_pos*= (exc_pos>0 && exc_pos<(int)Op->ExciteLength);
+			exc_pos *= (exc_pos>0 && exc_pos<=(int)Op->ExciteLength);
 //			if (n==0) cerr << numTS << " => " << Op->ExciteSignal[exc_pos] << endl;
 			volt[Op->E_Exc_dir[n]][Op->E_Exc_index[0][n]][Op->E_Exc_index[1][n]][Op->E_Exc_index[2][n]] += Op->E_Exc_amp[n]*Op->ExciteSignal[exc_pos];
 		}