diff --git a/imagecorruptions/corruptions.py b/imagecorruptions/corruptions.py
index cdab39c..c9e8d38 100644
--- a/imagecorruptions/corruptions.py
+++ b/imagecorruptions/corruptions.py
@@ -39,7 +39,7 @@ def plasma_fractal(mapsize=256, wibbledecay=3):
     'mapsize' must be a power of two.
     """
     assert (mapsize & (mapsize - 1) == 0)
-    maparray = np.empty((mapsize, mapsize), dtype=np.float_)
+    maparray = np.empty((mapsize, mapsize), dtype=np.float32)
     maparray[0, 0] = 0
     stepsize = mapsize
     wibble = 100