diff --git a/roaring/roaring.go b/roaring/roaring.go
index 86ee64fc5..ac49ee2f3 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -2033,18 +2033,18 @@ func (c *Container) runCountRange(start, end int32) (n int32) {
 			break
 		}
 		// iv is superset of range
-		if int32(iv.start) < start && int32(iv.last) > end {
+		if int32(iv.start) <= start && int32(iv.last) >= end {
 			return end - start
 		}
 		// iv is subset of range
-		if int32(iv.start) >= start && int32(iv.last) < end {
+		if int32(iv.start) >= start && int32(iv.last) <= end {
 			n += iv.runlen()
 		}
-		// iv overlaps beginning of range
+		// iv overlaps beginning of range without being a subset
 		if int32(iv.start) < start && int32(iv.last) < end {
 			n += int32(iv.last) - start + 1
 		}
-		// iv overlaps end of range
+		// iv overlaps end of range without being a subset
 		if int32(iv.start) > start && int32(iv.last) >= end {
 			n += end - int32(iv.start)
 		}
diff --git a/roaring/roaring_internal_test.go b/roaring/roaring_internal_test.go
index 0ecd73021..27fbe8f29 100644
--- a/roaring/roaring_internal_test.go
+++ b/roaring/roaring_internal_test.go
@@ -147,6 +147,16 @@ func TestRunCountRange(t *testing.T) {
 	c.add(10)
 	c.add(11)
 
+	cnt = c.runCountRange(4, 8)
+	if cnt != 3 {
+		t.Fatalf("should get 3 from range overlaps front of interval, but got: %v", cnt)
+	}
+
+	cnt = c.runCountRange(5, 8)
+	if cnt != 3 {
+		t.Fatalf("should get 3 from range within interval, but got: %v", cnt)
+	}
+
 	cnt = c.runCountRange(6, 8)
 	if cnt != 2 {
 		t.Fatalf("should get 2 from range within interval, but got: %v", cnt)
@@ -162,6 +172,31 @@ func TestRunCountRange(t *testing.T) {
 		t.Fatalf("should get 3 from range overlaps back of interval, but got: %v", cnt)
 	}
 
+	cnt = c.runCountRange(8, 10)
+	if cnt != 2 {
+		t.Fatalf("should get 2 from range within interval, but got: %v", cnt)
+	}
+
+	cnt = c.runCountRange(8, 11)
+	if cnt != 3 {
+		t.Fatalf("should get 3 from range within interval, but got: %v", cnt)
+	}
+
+	cnt = c.runCountRange(8, 12)
+	if cnt != 4 {
+		t.Fatalf("should get 4 from range overlaps back of interval, but got: %v", cnt)
+	}
+
+	cnt = c.runCountRange(5, 12)
+	if cnt != 7 {
+		t.Fatalf("should get 7 from interval within range, but got: %v", cnt)
+	}
+
+	cnt = c.runCountRange(5, 11)
+	if cnt != 6 {
+		t.Fatalf("should get 6 from interval equal to range, but got: %v", cnt)
+	}
+
 	c.add(17)
 	c.add(19)
 	c.add(18)
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index 836fd8de3..fbe952737 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -457,6 +457,12 @@ func TestBitmap_RunCountRange(t *testing.T) {
 	if n := bm2.CountRange(3, 2); n != 0 {
 		t.Fatalf("unexpected n: %d", n)
 	}
+
+	bm3 := roaring.NewFileBitmap(1, 2, 3, 4)
+	bm3.Optimize() // convert to runs
+	if n := bm3.CountRange(1, 3); n != 2 {
+		t.Fatalf("unexpected n: %d", n)
+	}
 }
 
 func TestBitmap_Intersection(t *testing.T) {