diff --git a/openpiv/pyprocess.py b/openpiv/pyprocess.py
index 201c0cb5..3cbc406f 100644
--- a/openpiv/pyprocess.py
+++ b/openpiv/pyprocess.py
@@ -873,7 +873,7 @@ def fft_correlate_windows(window_a, window_b,
     # works for rectangular windows as well
     x = [[1 , 0 , 0 , 0] , [0 , -1 , 0 , 0] , [0 , 0 , 3 , 0] ,
         [0 , 0 , 0 , 1], [0 , 0 , 0 , 1]]
-    x = np.array(x,dtype=np.float)
+    x = np.array(x,dtype=np.float64)
     y = [[4 , 5] , [3 , 4]]
     y = np.array(y)
     print ("conv:" ,  signal.convolve2d(x , y , 'full'))
diff --git a/pyproject.toml b/pyproject.toml
index bc2208b7..ef5275e6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,7 @@ classifiers = [
 
 [tool.poetry.dependencies]
 python = ">=3.10"
-numpy = "^1.21.6"
+numpy = ">=1.21.6"
 imageio = "^2.22.4"
 matplotlib = "^3"
 scikit-image=">=0.23"
diff --git a/setup.py b/setup.py
index 0fb2c5e7..6933a439 100644
--- a/setup.py
+++ b/setup.py
@@ -19,7 +19,7 @@
         'setuptools',
     ],
     install_requires=[
-        'numpy',
+        'numpy>=1.21.6',
         'imageio>=2.22.4',
         'matplotlib>=3',
         'scikit-image',