diff --git a/examples/demo_mandelbrot.py b/examples/demo_mandelbrot.py
index 1c04da612..69b30a1c5 100644
--- a/examples/demo_mandelbrot.py
+++ b/examples/demo_mandelbrot.py
@@ -38,7 +38,7 @@ def calc_fractal_opencl(q, maxiter):
     ctx = cl.create_some_context()
     queue = cl.CommandQueue(ctx)
 
-    output = np.empty(q.shape, dtype=np.uint16)
+    output = np.empty(q.shape, dtype=np.uint32)
 
     mf = cl.mem_flags
     q_opencl = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=q)
@@ -48,12 +48,13 @@ def calc_fractal_opencl(q, maxiter):
         ctx,
         """
     #pragma OPENCL EXTENSION cl_khr_byte_addressable_store : enable
-    __kernel void mandelbrot(__global float2 *q,
-                     __global ushort *output, ushort const maxiter)
+    #pragma OPENCL EXTENSION cl_khr_fp64 : enable
+    __kernel void mandelbrot(__global double2 *q,
+                     __global uint *output, uint const maxiter)
     {
         int gid = get_global_id(0);
-        float nreal, real = 0;
-        float imag = 0;
+        double nreal, real = 0;
+        double imag = 0;
 
         output[gid] = 0;
 
@@ -70,7 +71,7 @@ def calc_fractal_opencl(q, maxiter):
     ).build()
 
     prg.mandelbrot(
-        queue, output.shape, None, q_opencl, output_opencl, np.uint16(maxiter)
+        queue, output.shape, None, q_opencl, output_opencl, np.uint32(maxiter)
     )
 
     cl.enqueue_copy(queue, output, output_opencl).wait()
@@ -82,7 +83,7 @@ def calc_fractal_serial(q, maxiter):
     # calculate z using pure python on a numpy array
     # note that, unlike the other two implementations,
     # the number of iterations per point is NOT constant
-    z = np.zeros(q.shape, complex)
+    z = np.zeros(q.shape, np.complex128)
     output = np.resize(
         np.array(
             0,
@@ -107,7 +108,7 @@ def calc_fractal_numpy(q, maxiter):
         ),
         q.shape,
     )
-    z = np.zeros(q.shape, np.complex64)
+    z = np.zeros(q.shape, np.complex128)
 
     for it in range(maxiter):
         z = z * z + q
@@ -129,7 +130,7 @@ def draw(self, x1, x2, y1, y2, maxiter=30):
         # draw the Mandelbrot set, from numpy example
         xx = np.arange(x1, x2, (x2 - x1) / w)
         yy = np.arange(y2, y1, (y1 - y2) / h) * 1j
-        q = np.ravel(xx + yy[:, np.newaxis]).astype(np.complex64)
+        q = np.ravel(xx + yy[:, np.newaxis]).astype(np.complex128)
 
         start_main = time.time()
         output = calc_fractal(q, maxiter)