diff --git a/.github/workflows/gh_actions_ci.yml b/.github/workflows/gh_actions_ci.yml
index 5c4b053e..bbb00211 100644
--- a/.github/workflows/gh_actions_ci.yml
+++ b/.github/workflows/gh_actions_ci.yml
@@ -125,7 +125,7 @@ jobs:
       - name: Build
         shell: pwsh
         run: |
-          conda install -y python=3.10 git pybind11 numpy cmake llvmdev tbb-devel tbb astroquery libboost-devel fmt spdlog sleef sympy cloudpickle zlib libzlib 'mppp=1.*' numba
+          conda install -y python=3.10 git pybind11 numpy<2 cmake llvmdev tbb-devel tbb astroquery libboost-devel fmt spdlog sleef sympy cloudpickle zlib libzlib 'mppp=1.*' numba
           git clone --depth 1 https://github.com/bluescarni/heyoka.git heyoka_cpp
           cd heyoka_cpp
           mkdir build
diff --git a/tools/circleci_conda_heyoka_head_310.sh b/tools/circleci_conda_heyoka_head_310.sh
index 499fde14..06bf14e1 100644
--- a/tools/circleci_conda_heyoka_head_310.sh
+++ b/tools/circleci_conda_heyoka_head_310.sh
@@ -14,7 +14,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniforge/bin:$PATH"
 bash miniforge.sh -b -p $HOME/miniforge
-mamba create -y -p $deps_dir python=3.10 c-compiler cxx-compiler git pybind11 numpy mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog myst-nb matplotlib sympy scipy pykep cloudpickle 'sphinx=7.*' 'sphinx-book-theme=1.*'
+mamba create -y -p $deps_dir python=3.10 c-compiler cxx-compiler git pybind11 'numpy<2' mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog myst-nb matplotlib sympy scipy pykep cloudpickle 'sphinx=7.*' 'sphinx-book-theme=1.*'
 source activate $deps_dir
 
 export HEYOKA_PY_PROJECT_DIR=`pwd`
diff --git a/tools/circleci_conda_heyoka_head_312.sh b/tools/circleci_conda_heyoka_head_312.sh
index 1151160d..1cce08fa 100644
--- a/tools/circleci_conda_heyoka_head_312.sh
+++ b/tools/circleci_conda_heyoka_head_312.sh
@@ -14,7 +14,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniforge/bin:$PATH"
 bash miniforge.sh -b -p $HOME/miniforge
-mamba create -y -p $deps_dir python=3.12 c-compiler cxx-compiler git pybind11 numpy mpmath cmake llvmdev tbb-devel tbb libboost-devel 'mppp=1.*' sleef fmt spdlog sympy cloudpickle
+mamba create -y -p $deps_dir python=3.12 c-compiler cxx-compiler git pybind11 'numpy<2' mpmath cmake llvmdev tbb-devel tbb libboost-devel 'mppp=1.*' sleef fmt spdlog sympy cloudpickle
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.
diff --git a/tools/circleci_conda_heyoka_head_39.sh b/tools/circleci_conda_heyoka_head_39.sh
index c353beeb..b94ea439 100644
--- a/tools/circleci_conda_heyoka_head_39.sh
+++ b/tools/circleci_conda_heyoka_head_39.sh
@@ -14,7 +14,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniforge/bin:$PATH"
 bash miniforge.sh -b -p $HOME/miniforge
-mamba create -y -p $deps_dir python=3.9 c-compiler cxx-compiler git pybind11 numpy mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog myst-nb matplotlib sympy scipy pykep cloudpickle 'sphinx=7.*' 'sphinx-book-theme=1.*'
+mamba create -y -p $deps_dir python=3.9 c-compiler cxx-compiler git pybind11 'numpy<2' mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog myst-nb matplotlib sympy scipy pykep cloudpickle 'sphinx=7.*' 'sphinx-book-theme=1.*'
 source activate $deps_dir
 
 export HEYOKA_PY_PROJECT_DIR=`pwd`
diff --git a/tools/circleci_ubuntu_arm64.sh b/tools/circleci_ubuntu_arm64.sh
index 05a1f0aa..fb4abdcb 100644
--- a/tools/circleci_ubuntu_arm64.sh
+++ b/tools/circleci_ubuntu_arm64.sh
@@ -14,7 +14,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniforge/bin:$PATH"
 bash miniforge.sh -b -p $HOME/miniforge
-mamba create -y -q -p $deps_dir cxx-compiler c-compiler cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog python=3.10 pybind11 numpy mpmath sympy scipy cloudpickle myst-nb matplotlib 'sphinx=7.*' 'sphinx-book-theme=1.*'
+mamba create -y -q -p $deps_dir cxx-compiler c-compiler cmake llvmdev tbb-devel tbb astroquery libboost-devel 'mppp=1.*' sleef fmt spdlog python=3.10 pybind11 'numpy<2' mpmath sympy scipy cloudpickle myst-nb matplotlib 'sphinx=7.*' 'sphinx-book-theme=1.*'
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.
diff --git a/tools/gha_conda_docs.sh b/tools/gha_conda_docs.sh
index 8d410ecb..f5a23e07 100644
--- a/tools/gha_conda_docs.sh
+++ b/tools/gha_conda_docs.sh
@@ -15,7 +15,7 @@ export deps_dir=$HOME/local
 export PATH="$HOME/miniforge/bin:$PATH"
 bash miniforge.sh -b -p $HOME/miniforge
 mamba create -y -p $deps_dir c-compiler cxx-compiler python=3.10 git pybind11 \
-    ninja numpy mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel \
+    ninja 'numpy<2' mpmath cmake llvmdev tbb-devel tbb astroquery libboost-devel \
     'mppp=1.*' sleef fmt spdlog myst-nb matplotlib sympy scipy pykep cloudpickle \
     'sphinx=7.*' 'sphinx-book-theme=1.*'
 source activate $deps_dir
diff --git a/tools/gha_conda_static.sh b/tools/gha_conda_static.sh
index d52066c4..56e39c18 100755
--- a/tools/gha_conda_static.sh
+++ b/tools/gha_conda_static.sh
@@ -16,7 +16,7 @@ export PATH="$HOME/miniconda/bin:$PATH"
 bash miniconda.sh -b -p $HOME/miniconda
 conda config --add channels conda-forge
 conda config --set channel_priority strict
-conda create -y -q -p $deps_dir python=3.10 git pybind11 numpy mpmath cmake llvmdev tbb-devel tbb libboost-devel 'mppp=1.*' sleef fmt spdlog sympy cloudpickle c-compiler cxx-compiler numba zlib
+conda create -y -q -p $deps_dir python=3.10 git pybind11 'numpy<2' mpmath cmake llvmdev tbb-devel tbb libboost-devel 'mppp=1.*' sleef fmt spdlog sympy cloudpickle c-compiler cxx-compiler numba zlib
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.
diff --git a/tools/gha_osx_heyoka_head.sh b/tools/gha_osx_heyoka_head.sh
index 2e8ea6ae..4064eb5f 100644
--- a/tools/gha_osx_heyoka_head.sh
+++ b/tools/gha_osx_heyoka_head.sh
@@ -11,7 +11,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniconda/bin:$PATH"
 bash miniconda.sh -b -p $HOME/miniconda
-mamba create -y -p $deps_dir python=3.11 c-compiler cxx-compiler git pybind11 numpy cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef fmt spdlog sympy cloudpickle 'mppp=1.*'
+mamba create -y -p $deps_dir python=3.11 c-compiler cxx-compiler git pybind11 'numpy<2' cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef fmt spdlog sympy cloudpickle 'mppp=1.*'
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.
diff --git a/tools/gha_osx_heyoka_head_static.sh b/tools/gha_osx_heyoka_head_static.sh
index e279052a..019724d0 100644
--- a/tools/gha_osx_heyoka_head_static.sh
+++ b/tools/gha_osx_heyoka_head_static.sh
@@ -11,7 +11,7 @@ wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge
 export deps_dir=$HOME/local
 export PATH="$HOME/miniconda/bin:$PATH"
 bash miniconda.sh -b -p $HOME/miniconda
-mamba create -y -p $deps_dir python=3.11 c-compiler cxx-compiler git pybind11 numpy cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef fmt spdlog sympy cloudpickle 'mppp=1.*' numba
+mamba create -y -p $deps_dir python=3.11 c-compiler cxx-compiler git pybind11 'numpy<2' cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef fmt spdlog sympy cloudpickle 'mppp=1.*' numba
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.
diff --git a/tools/gha_osx_heyoka_stable.sh b/tools/gha_osx_heyoka_stable.sh
index 4ef7aae2..a4f1b9f4 100644
--- a/tools/gha_osx_heyoka_stable.sh
+++ b/tools/gha_osx_heyoka_stable.sh
@@ -13,7 +13,7 @@ export PATH="$HOME/miniconda/bin:$PATH"
 bash miniconda.sh -b -p $HOME/miniconda
 conda create -y -q -p $deps_dir
 source activate $deps_dir
-mamba install -y python=3.10 pybind11 numpy cmake heyoka libboost-devel
+mamba install -y python=3.10 pybind11 'numpy<2' cmake heyoka libboost-devel
 
 # Create the build dir and cd into it.
 mkdir build
diff --git a/tools/travis_ubuntu_ppc64.sh b/tools/travis_ubuntu_ppc64.sh
index 5e35cc56..363c7d13 100755
--- a/tools/travis_ubuntu_ppc64.sh
+++ b/tools/travis_ubuntu_ppc64.sh
@@ -11,7 +11,7 @@ curl -L -o miniconda.sh https://github.com/conda-forge/miniforge/releases/latest
 export deps_dir=$HOME/local
 export PATH="$HOME/miniconda/bin:$PATH"
 bash miniconda.sh -b -p $HOME/miniconda
-conda create -y -q -p $deps_dir cxx-compiler c-compiler cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef xtensor xtensor-blas blas blas-devel fmt spdlog python pybind11 numpy mpmath sympy cloudpickle mppp git make
+conda create -y -q -p $deps_dir cxx-compiler c-compiler cmake llvmdev tbb-devel tbb astroquery libboost-devel sleef xtensor xtensor-blas blas blas-devel fmt spdlog python pybind11 'numpy<2' mpmath sympy cloudpickle mppp git make
 source activate $deps_dir
 
 # Checkout, build and install heyoka's HEAD.