diff --git a/pkgs/development/python-modules/httpx/setup-hook.sh b/pkgs/development/python-modules/httpx/setup-hook.sh
index 7e9ced07b69c..fe567877ef1a 100644
--- a/pkgs/development/python-modules/httpx/setup-hook.sh
+++ b/pkgs/development/python-modules/httpx/setup-hook.sh
@@ -1,5 +1,7 @@
 httpxSslCertFileUnset() {
+  if [ ! -e "${SSL_CERT_FILE-}" ]; then
     unset SSL_CERT_FILE
+  fi
 }
 
 postHooks+=(httpxSslCertFileUnset)
diff --git a/pkgs/development/python-modules/prowlpy/default.nix b/pkgs/development/python-modules/prowlpy/default.nix
index f69da1bc04c0..a6368e345efe 100644
--- a/pkgs/development/python-modules/prowlpy/default.nix
+++ b/pkgs/development/python-modules/prowlpy/default.nix
@@ -43,6 +43,7 @@ buildPythonPackage (finalAttrs: {
   pythonImportsCheck = [ "prowlpy" ];
 
   nativeCheckInputs = [
+    cacert
     pytest-asyncio
     pytest-cov-stub
     pytestCheckHook
@@ -50,12 +51,6 @@ buildPythonPackage (finalAttrs: {
   ]
   ++ lib.concatAttrValues finalAttrs.passthru.optional-dependencies;
 
-  preCheck = ''
-    # Without this pyreqwest fails with
-    #     unexpected error: No CA certificates were loaded from the system
-    export SSL_CERT_FILE="${cacert}/etc/ssl/certs/ca-bundle.crt"
-  '';
-
   # tests fail without this
   pytestFlags = [ "-v" ];
 
diff --git a/pkgs/development/python-modules/pyreqwest/default.nix b/pkgs/development/python-modules/pyreqwest/default.nix
index 10b189757108..3d6fe0e9c825 100644
--- a/pkgs/development/python-modules/pyreqwest/default.nix
+++ b/pkgs/development/python-modules/pyreqwest/default.nix
@@ -43,6 +43,7 @@ buildPythonPackage (finalAttrs: {
   pythonImportsCheck = [ "pyreqwest" ];
 
   nativeCheckInputs = [
+    cacert
     dirty-equals
     docker
     granian
@@ -57,12 +58,6 @@ buildPythonPackage (finalAttrs: {
     yarl
   ];
 
-  preCheck = ''
-    # Without this tests fails with
-    #     unexpected error: No CA certificates were loaded from the system
-    export SSL_CERT_FILE="${cacert}/etc/ssl/certs/ca-bundle.crt"
-  '';
-
   disabledTestPaths = [
     # requires a running Docker daemon
     "tests/test_examples.py"