diff --git a/pyproject.toml b/pyproject.toml
index f8cf47e..4f4153d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,8 +53,8 @@ documentation = "http://spherical-geometry.readthedocs.io/"
 requires = [
     "setuptools>=61.2",
     "setuptools_scm[toml]>=3.6",
-    #"numpy>=1.25",
-    "numpy>=2.0.0dev0",
+    "numpy>=1.25",
+    #"numpy>=2.0.0dev0",
 ]
 build-backend = "setuptools.build_meta"
 
diff --git a/spherical_geometry/great_circle_arc.py b/spherical_geometry/great_circle_arc.py
index b9716df..7776e8c 100644
--- a/spherical_geometry/great_circle_arc.py
+++ b/spherical_geometry/great_circle_arc.py
@@ -19,7 +19,7 @@
 # the python versions are a fallback if the C cannot be used
 try:
     from spherical_geometry import math_util
-    HAS_C_UFUNCS = True
+    HAS_C_UFUNCS = False
 except ImportError:
     HAS_C_UFUNCS = False