diff --git a/include/c3d/maths.h b/include/c3d/maths.h
index b3aade8..a935587 100644
--- a/include/c3d/maths.h
+++ b/include/c3d/maths.h
@@ -346,9 +346,10 @@ static inline C3D_FVec Mtx_MultiplyFVecH(const C3D_Mtx* mtx, C3D_FVec v)
 /**
  * @brief 3D translation
  * @param[in,out] mtx Matrix to translate
- * @param[in]     x   X component to translate
- * @param[in]     y   Y component to translate
- * @param[in]     z   Z component to translate
+ * @param[in]     x            X component to translate
+ * @param[in]     y            Y component to translate
+ * @param[in]     z            Z component to translate
+ * @param[in]     bRightSide   Whether to transform from the right side
  */
 void Mtx_Translate(C3D_Mtx* mtx, float x, float y, float z, bool bRightSide);
 
diff --git a/source/maths/mtx_multiply.c b/source/maths/mtx_multiply.c
index c7e6377..f7d5b54 100644
--- a/source/maths/mtx_multiply.c
+++ b/source/maths/mtx_multiply.c
@@ -2,6 +2,15 @@
 
 void Mtx_Multiply(C3D_Mtx* out, const C3D_Mtx* a, const C3D_Mtx* b)
 {
+	// if out is a or b, then we need to avoid overwriting them
+	if(out == a || out == b)
+	{
+		C3D_Mtx tmp;
+		Mtx_Multiply(&tmp, a, b);
+		Mtx_Copy(out, &tmp);
+		return;
+	}
+
 	// http://www.wolframalpha.com/input/?i={{a,b,c,d},{e,f,g,h},{i,j,k,l},{m,n,o,p}}{{α,β,γ,δ},{ε,θ,ι,κ},{λ,μ,ν,ξ},{ο,π,ρ,σ}}
 	int i, j;
 	for (j = 0; j < 4; ++j)