diff --git a/src/simulation/Simulation.cpp b/src/simulation/Simulation.cpp
index 0c22c4d55..76796e39b 100644
--- a/src/simulation/Simulation.cpp
+++ b/src/simulation/Simulation.cpp
@@ -2987,25 +2987,35 @@ int Simulation::is_boundary(int pt, int x, int y)
 	return 1;
 }
 
-int Simulation::find_next_boundary(int pt, int *x, int *y, int dm, int *em)
+int Simulation::find_next_boundary(int pt, int *x, int *y, int dm, int *em, bool reverse)
 {
 	static int dx[8] = {1,1,0,-1,-1,-1,0,1};
 	static int dy[8] = {0,1,1,1,0,-1,-1,-1};
 	static int de[8] = {0x83,0x07,0x0E,0x1C,0x38,0x70,0xE0,0xC1};
-	int i, ii, i0;
 
 	if (*x <= 0 || *x >= XRES-1 || *y <= 0 || *y >= YRES-1)
+	{
 		return 0;
+	}
 
-	if (*em != -1) {
-		i0 = *em;
-		dm &= de[i0];
-	} else
-		i0 = 0;
+	if (*em != -1)
+	{
+		dm &= de[*em];
+	}
 
-	for (ii=0; ii<8; ii++) {
-		i = (ii + i0) & 7;
-		if ((dm & (1 << i)) && is_boundary(pt, *x+dx[i], *y+dy[i])) {
+	unsigned int mask = 0;
+	for (int i = 0; i < 8; ++i)
+	{
+		if ((dm & (1U << i)) && is_blocking(pt, *x + dx[i], *y + dy[i]))
+		{
+			mask |= (1U << i);
+		}
+	}
+	for (int i = 0; i < 8; ++i)
+	{
+		int n = (i + (reverse ? 1 : -1)) & 7;
+		if (((mask & (1U << i))) && !(mask & (1U << n)))
+		{
 			*x += dx[i];
 			*y += dy[i];
 			*em = i;
@@ -3039,9 +3049,9 @@ int Simulation::get_normal(int pt, int x, int y, float dx, float dy, float *nx,
 	j = 0;
 	for (i=0; i<SURF_RANGE; i++) {
 		if (lv)
-			lv = find_next_boundary(pt, &lx, &ly, ldm, &lm);
+			lv = find_next_boundary(pt, &lx, &ly, ldm, &lm, true);
 		if (rv)
-			rv = find_next_boundary(pt, &rx, &ry, rdm, &rm);
+			rv = find_next_boundary(pt, &rx, &ry, rdm, &rm, false);
 		j += lv + rv;
 		if (!lv && !rv)
 			break;
@@ -3052,7 +3062,6 @@ int Simulation::get_normal(int pt, int x, int y, float dx, float dy, float *nx,
 
 	if ((lx == rx) && (ly == ry))
 		return 0;
-
 	ex = float(rx - lx);
 	ey = float(ry - ly);
 	r = 1.0f/hypot(ex, ey);
diff --git a/src/simulation/Simulation.h b/src/simulation/Simulation.h
index a1282c4ca..3671dfc31 100644
--- a/src/simulation/Simulation.h
+++ b/src/simulation/Simulation.h
@@ -129,7 +129,7 @@ public:
 
 	int is_blocking(int t, int x, int y);
 	int is_boundary(int pt, int x, int y);
-	int find_next_boundary(int pt, int *x, int *y, int dm, int *em);
+	int find_next_boundary(int pt, int *x, int *y, int dm, int *em, bool reverse);
 	void photoelectric_effect(int nx, int ny);
 	unsigned direction_to_map(float dx, float dy, int t);
 	int do_move(int i, int x, int y, float nxf, float nyf);