diff --git a/src/windows/guest.c b/src/windows/guest.c
index 916c3e2608..4d8bbf93b7 100644
--- a/src/windows/guest.c
+++ b/src/windows/guest.c
@@ -1209,10 +1209,8 @@ void window_guest_overview_tool_down(){
 		return;
 	}
 
-	int _edx = dest_z >> 3;
-	_edx &= 0xFFFF00FF;
-	_edx |= dest_z << 8;
-	_edx += 0x100;
+	int _edx;
+	_edx = (dest_z / 8) | (((dest_z / 8) + 1) << 8);
 	int flags = RCT2_CALLPROC_X(0x68B93A, tile_x, 0xF, tile_y, _edx, (int)w, 0, 0);
 
 	if (flags & 0x100){
diff --git a/src/windows/staff.c b/src/windows/staff.c
index 9176abacb0..4639a6bd68 100644
--- a/src/windows/staff.c
+++ b/src/windows/staff.c
@@ -1129,10 +1129,8 @@ void window_staff_overview_tool_down(){
 			return;
 		}
 
-		int _edx = dest_z >> 3;
-		_edx &= 0xFFFF00FF;
-		_edx |= (_edx & 0xFF) << 8;
-		_edx += 0x100;
+		int _edx;
+		_edx = (dest_z / 8) | (((dest_z / 8) + 1) << 8);
 		int flags = RCT2_CALLPROC_X(0x68B93A, tile_x, 0xF, tile_y, _edx, (int)w, 0, 0);
 
 		if (flags & 0x100){