diff --git a/source/core/interpolate.cpp b/source/core/interpolate.cpp
index 8601b25b7..ea79c8817 100644
--- a/source/core/interpolate.cpp
+++ b/source/core/interpolate.cpp
@@ -61,6 +61,7 @@ double Get(int index, int type)
 
 void Set(int index, int type, double val)
 {
+	int old;
 	switch(type)
 	{
 	case Interp_Sect_Floorz:			sector[index].floorz = xs_CRoundToInt(val); break;
@@ -72,8 +73,8 @@ void Set(int index, int type, double val)
 	case Interp_Sect_CeilingPanX:       sector[index].ceilingxpan_ = float(val); break;
 	case Interp_Sect_CeilingPanY:       sector[index].ceilingypan_ = float(val); break;
                                         
-	case Interp_Wall_X:                 wall[index].x = xs_CRoundToInt(val); sector[wall[index].sector].dirty = 255; break;
-	case Interp_Wall_Y:                 wall[index].y = xs_CRoundToInt(val); sector[wall[index].sector].dirty = 255; break;
+	case Interp_Wall_X:                 old = wall[index].x; wall[index].x = xs_CRoundToInt(val); if (wall[index].x != old) sector[wall[index].sector].dirty = 255; break;
+	case Interp_Wall_Y:                 old = wall[index].y; wall[index].y = xs_CRoundToInt(val); if (wall[index].y != old) sector[wall[index].sector].dirty = 255; break;
 	case Interp_Wall_PanX:              wall[index].xpan_ = float(val);  break;
 	case Interp_Wall_PanY:              wall[index].ypan_ = float(val);  break;