diff --git a/pyproject.toml b/pyproject.toml
index ff9c04c..db2f468 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,7 +29,7 @@ classifiers = [
 ]
 dependencies = [
   "ipywidgets>=8.0.0",
-  "numpy",
+  "numpy<2.0.0",
   "widget_code_input",
   "matplotlib",
   "termcolor"
diff --git a/tox.ini b/tox.ini
index bedf882..4256ae2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,7 +35,7 @@ deps =
     imageio
     # we fix matplotlib for consistent image tests
     matplotlib==3.7.2
-    numpy
+    numpy<2.0.0
     scikit-image
     ipympl
 commands =
@@ -67,7 +67,7 @@ deps =
     imageio
     # we fix matplotlib for consistent image tests
     matplotlib==3.7.2
-    numpy
+    numpy<2.0.0
     scikit-image
     ipympl
 commands =