diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index a14dffb..43a51fe 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -20,7 +20,7 @@ jobs:
     if: github.event.pull_request.draft == false
     runs-on: ubuntu-latest
     container:
-      image: ghcr.io/faasm/cpython:0.4.0
+      image: ghcr.io/faasm/cpython:0.5.0
     steps:
       - name: "Fetch code"
         uses: actions/checkout@v4
@@ -41,7 +41,7 @@ jobs:
       REDIS_QUEUE_HOST: redis
       REDIS_STATE_HOST: redis
     container:
-      image: ghcr.io/faasm/cpython:0.4.0
+      image: ghcr.io/faasm/cpython:0.5.0
     services:
       redis:
         image: redis
diff --git a/Dockerfile b/Dockerfile
index 45e8dde..e91f343 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,19 @@
-FROM ghcr.io/faasm/cpp-sysroot:0.4.0
+FROM ghcr.io/faasm/cpp-sysroot:0.8.0
 ARG FAASM_PYTHON_VERSION
 
 SHELL ["/bin/bash", "-c"]
 ENV PYTHON_DOCKER="on"
 
-RUN apt update && apt install -y libssl-dev
+RUN apt update \
+    && apt install -y --no-install-recommends \
+        dpkg-dev \
+        libssl-dev \
+        pkg-config \
+        wget \
+        zlib1g \
+        zlib1g-dev \
+  && apt autoremove -y \
+  && apt clean; rm -rf /var/lib/apt/lists/*
 
 # Clone code and submodules
 RUN mkdir -p /code \
@@ -30,21 +39,21 @@ RUN cd /code/python \
         cpython.func
 
 # Build cross-compiled python modules, including `pyfaasm`
-RUN cd /code/python \
-    && ./bin/crossenv_setup.sh \
-    && source ./cross_venv/bin/activate \
-    && pip3 install -r crossenv/requirements.txt \
-    && inv -r crossenv modules.build
+# RUN cd /code/python \
+    #     && ./bin/crossenv_setup.sh \
+    #     && source ./cross_venv/bin/activate \
+    #     && pip3 install -r crossenv/requirements.txt \
+    #     && inv -r crossenv modules.build
 
-# Finally, install the cross-compiled Python modules
-RUN cd /code/python \
-    && source ./venv/bin/activate \
-    && inv modules.install
+# # Finally, install the cross-compiled Python modules
+# RUN cd /code/python \
+    #     && source ./venv/bin/activate \
+    #     && inv modules.install
 
 # TODO: Install experimental pacakges
 # RUN . ./cross_venv/bin/activate && inv libs.install --experimental
 
 WORKDIR /code/python
-ENV TERM xterm-256color
+ENV TERM=xterm-256color
 RUN sed -i 's/\/code\/cpp\/bin/\/code\/python\/bin/g' ~/.bashrc
 CMD ["/bin/bash", "-l"]
diff --git a/VERSION b/VERSION
index 1d0ba9e..8f0916f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.4.0
+0.5.0
diff --git a/pyfaasm/pyfaasm/core.py b/pyfaasm/pyfaasm/core.py
index 8e4491a..5c3d59f 100644
--- a/pyfaasm/pyfaasm/core.py
+++ b/pyfaasm/pyfaasm/core.py
@@ -16,8 +16,6 @@
 
 
 def get_env_bool(var_name):
-    global env_cache
-
     if var_name not in env_cache:
         value = os.environ.get(var_name)
         env_cache[var_name] = bool(value)
@@ -26,7 +24,6 @@ def get_env_bool(var_name):
 
 
 def set_env_bool(var_name, value):
-    global env_cache
     env_cache[var_name] = value
 
 
@@ -76,7 +73,6 @@ def write_output(output):
 
 def get_output():
     if is_local_output():
-        global output_data
         return output_data
     else:
         raise RuntimeError(
diff --git a/requirements.txt b/requirements.txt
index dda3f9e..3bf94e7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,5 @@
-black==22.3.0
-faasmctl==0.13.0
-flake8==3.9.2
+black>=23.12.0
+faasmctl>=0.51.0
+flake8>=7.0.0
 invoke>=2.0.0
-numpy==1.22.0
 requests>=2.31.0