diff --git a/GlmToolkit.cpp b/GlmToolkit.cpp
index 648f4b8..04e5916 100644
--- a/GlmToolkit.cpp
+++ b/GlmToolkit.cpp
@@ -81,11 +81,6 @@ GlmToolkit::AxisAlignedBoundingBox::AxisAlignedBoundingBox(const GlmToolkit::Axi
 {
 }
 
-void GlmToolkit::AxisAlignedBoundingBox::operator = (const GlmToolkit::AxisAlignedBoundingBox &D ) {
-    mMin = D.mMin;
-    mMax = D.mMax;
-}
-
 void GlmToolkit::AxisAlignedBoundingBox::extend(const glm::vec3& point)
 {
     if (isNull()) {
@@ -252,6 +247,16 @@ bool GlmToolkit::operator< (const GlmToolkit::AxisAlignedBoundingBox& A, const G
     return ( glm::length2(A.mMax-A.mMin) < glm::length2(B.mMax-B.mMin) );
 }
 
+GlmToolkit::AxisAlignedBoundingBox& GlmToolkit::AxisAlignedBoundingBox::operator = (const GlmToolkit::AxisAlignedBoundingBox &D )
+{
+    if (this != &D) {
+        this->mMin = D.mMin;
+        this->mMax = D.mMax;
+    }
+    return *this;
+}
+
+
 glm::ivec2 GlmToolkit::resolutionFromDescription(int aspectratio, int height)
 {
     int ar = glm::clamp(aspectratio, 0, 5);
diff --git a/GlmToolkit.h b/GlmToolkit.h
index fb25305..62241f6 100644
--- a/GlmToolkit.h
+++ b/GlmToolkit.h
@@ -16,7 +16,7 @@ class AxisAlignedBoundingBox
 public:
     AxisAlignedBoundingBox();
     AxisAlignedBoundingBox(const AxisAlignedBoundingBox &D);
-    void operator = (const AxisAlignedBoundingBox &D );
+    AxisAlignedBoundingBox& operator = (const AxisAlignedBoundingBox &D );
 
     // test
     inline bool isNull() const { return mMin.x > mMax.x || mMin.y > mMax.y || mMin.z > mMax.z;}