diff --git a/spine-c/src/spine/Bone.c b/spine-c/src/spine/Bone.c
index 9762e1c9f..ec51a635d 100644
--- a/spine-c/src/spine/Bone.c
+++ b/spine-c/src/spine/Bone.c
@@ -84,11 +84,7 @@ void Bone_updateWorldTransform (Bone* self, int flipX, int flipY) {
 		CONST_CAST(float, self->m00) = -self->m00;
 		CONST_CAST(float, self->m01) = -self->m01;
 	}
-	if (flipY) {
-		CONST_CAST(float, self->m10) = -self->m10;
-		CONST_CAST(float, self->m11) = -self->m11;
-	}
-	if (yDown) {
+	if (flipY != yDown) {
 		CONST_CAST(float, self->m10) = -self->m10;
 		CONST_CAST(float, self->m11) = -self->m11;
 	}
diff --git a/spine-csharp/src/Bone.cs b/spine-csharp/src/Bone.cs
index c395665fc..9a728b9be 100644
--- a/spine-csharp/src/Bone.cs
+++ b/spine-csharp/src/Bone.cs
@@ -87,11 +87,7 @@ namespace Spine {
 				M00 = -M00;
 				M01 = -M01;
 			}
-			if (flipY) {
-				M10 = -M10;
-				M11 = -M11;
-			}
-			if (yDown) {
+			if (flipY != yDown) {
 				M10 = -M10;
 				M11 = -M11;
 			}
diff --git a/spine-js/spine.js b/spine-js/spine.js
index 32015a275..3b53dd5a6 100644
--- a/spine-js/spine.js
+++ b/spine-js/spine.js
@@ -60,11 +60,7 @@ spine.Bone.prototype = {
 			this.m00 = -this.m00;
 			this.m01 = -this.m01;
 		}
-		if (flipY) {
-			this.m10 = -this.m10;
-			this.m11 = -this.m11;
-		}
-		if (spine.Bone.yDown) {
+		if (flipY != spine.Bone.yDown) {
 			this.m10 = -this.m10;
 			this.m11 = -this.m11;
 		}