diff --git a/engines/ultima/ultima8/world/sort_item.h b/engines/ultima/ultima8/world/sort_item.h
index 482e3eeeafa..3f69dbcb448 100644
--- a/engines/ultima/ultima8/world/sort_item.h
+++ b/engines/ultima/ultima8/world/sort_item.h
@@ -326,8 +326,8 @@ inline bool SortItem::overlap(const SortItem &si2) const {
 	// 'normal' of bot right line (-2, 1) of the bounding box
 	const int32 dot_bot_right = -point_bot_diff[0] - point_bot_diff[1] * 2;
 
-	const bool right_clear = _sxRight < si2._sxLeft;
-	const bool left_clear = _sxLeft > si2._sxRight;
+	const bool right_clear = _sxRight <= si2._sxLeft;
+	const bool left_clear = _sxLeft >= si2._sxRight;
 	const bool top_left_clear = dot_top_left >= 0;
 	const bool top_right_clear = dot_top_right >= 0;
 	const bool bot_left_clear = dot_bot_left >= 0;
diff --git a/test/engines/ultima/ultima8/world/sort_item.h b/test/engines/ultima/ultima8/world/sort_item.h
index 8515e6ba681..4bac9d77f2d 100644
--- a/test/engines/ultima/ultima8/world/sort_item.h
+++ b/test/engines/ultima/ultima8/world/sort_item.h
@@ -536,7 +536,6 @@ class U8SortItemTestSuite : public CxxTest::TestSuite {
 		si2._solid = true;
 
 		// Due to screenspace calculation changes these no longer overlap
-		// !TODO: Investigate overlap as it slightly differs from contains
 		//TS_ASSERT(si1.overlap(si2));
 		//TS_ASSERT(si2.overlap(si1));
 
@@ -587,14 +586,18 @@ class U8SortItemTestSuite : public CxxTest::TestSuite {
 		TS_ASSERT(!si2.below(si1));
 	}
 
-	/* Overlapping non-flat occludes flat */
 	void test_basic_occludes() {
 		Ultima::Ultima8::SortItem si1;
 		Ultima::Ultima8::SortItem si2;
 
 		Ultima::Ultima8::Box b1(0, 0, 0, 128, 128, 16);
-		Ultima::Ultima8::Box b2(0, 0, 0, 128, 128, 0);
 		si1.setBoxBounds(b1, 0, 0);
+		si2.setBoxBounds(b1, 0, 0);
+
+		TS_ASSERT(si1.occludes(si2));
+		TS_ASSERT(si2.occludes(si1));
+
+		Ultima::Ultima8::Box b2(0, 0, 0, 128, 128, 0);
 		si2.setBoxBounds(b2, 0, 0);
 
 		TS_ASSERT(si1.occludes(si2));
@@ -665,4 +668,66 @@ class U8SortItemTestSuite : public CxxTest::TestSuite {
 		TS_ASSERT(!si1.contains(si1._sxTop + 1, si1._syTop));
 		TS_ASSERT(!si1.contains(si1._sxTop - 1, si1._syTop));
 	}
+
+	void test_basic_overlap() {
+		Ultima::Ultima8::SortItem si1;
+		Ultima::Ultima8::SortItem si2;
+
+		Ultima::Ultima8::Box b1(0, 0, 0, 128, 128, 16);
+		si1.setBoxBounds(b1, 0, 0);
+		si2.setBoxBounds(b1, 0, 0);
+
+		TS_ASSERT(si1.overlap(si2));
+		TS_ASSERT(si2.overlap(si1));
+
+		Ultima::Ultima8::Box b2(0, 0, 0, 128, 128, 0);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(si1.overlap(si2));
+		TS_ASSERT(si2.overlap(si1));
+
+		// Check outside bounds using flats
+		b1 = Ultima::Ultima8::Box(0, 0, 0, 128, 128, 0);
+		si1.setBoxBounds(b1, 0, 0);
+
+		b2 = Ultima::Ultima8::Box(128, 0, 0, 128, 128, 0);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+
+		b2 = Ultima::Ultima8::Box(-128, 0, 0, 128, 128, 0);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+
+		b2 = Ultima::Ultima8::Box(0, 128, 0, 128, 128, 0);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+
+		b2 = Ultima::Ultima8::Box(0, -128, 0, 128, 128, 0);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+
+		// Check outside left & right bounds using non-flats
+		b1 = Ultima::Ultima8::Box(0, 0, 0, 128, 128, 32);
+		si1.setBoxBounds(b1, 0, 0);
+
+		b2 = Ultima::Ultima8::Box(128, -128, 0, 128, 128, 32);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+
+		b2 = Ultima::Ultima8::Box(-128, 128, 0, 128, 128, 32);
+		si2.setBoxBounds(b2, 0, 0);
+
+		TS_ASSERT(!si1.overlap(si2));
+		TS_ASSERT(!si2.overlap(si1));
+	}
 };