diff --git a/include/c3d/maths.h b/include/c3d/maths.h
index f9edd2f..e0d3ec7 100644
--- a/include/c3d/maths.h
+++ b/include/c3d/maths.h
@@ -296,7 +296,7 @@ void Mtx_Identity(C3D_Mtx* out);
  * @param[in]  a   Multiplicand
  * @param[in]  b   Multiplier
  */
-void Mtx_Multiply(C3D_Mtx* restrict out, const C3D_Mtx* a, const C3D_Mtx* b);
+void Mtx_Multiply(C3D_Mtx* __restrict out, const C3D_Mtx* a, const C3D_Mtx* b);
 
 /**
  * @brief Inverse a matrix
diff --git a/source/maths/mtx_multiply.c b/source/maths/mtx_multiply.c
index 8d69cb4..5182efa 100644
--- a/source/maths/mtx_multiply.c
+++ b/source/maths/mtx_multiply.c
@@ -1,6 +1,6 @@
 #include <c3d/maths.h>
 
-void Mtx_Multiply(C3D_Mtx* restrict out, const C3D_Mtx* a, const C3D_Mtx* b)
+void Mtx_Multiply(C3D_Mtx* __restrict out, const C3D_Mtx* a, const C3D_Mtx* b)
 {
 	// 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;