diff --git a/plugins/python-build/test/cache.bats b/plugins/python-build/test/cache.bats
index d8f8662b..1dca44b0 100644
--- a/plugins/python-build/test/cache.bats
+++ b/plugins/python-build/test/cache.bats
@@ -3,7 +3,7 @@
 load test_helper
 export PYTHON_BUILD_SKIP_MIRROR=1
 export PYTHON_BUILD_CACHE_PATH="$TMP/cache"
-unset PYTHON_BUILD_ARIA2_OPTS
+export PYTHON_BUILD_ARIA2_OPTS=
 
 setup() {
   mkdir "$PYTHON_BUILD_CACHE_PATH"
diff --git a/plugins/python-build/test/checksum.bats b/plugins/python-build/test/checksum.bats
index 1af9c722..ffb7d32b 100644
--- a/plugins/python-build/test/checksum.bats
+++ b/plugins/python-build/test/checksum.bats
@@ -3,7 +3,7 @@
 load test_helper
 export PYTHON_BUILD_SKIP_MIRROR=1
 export PYTHON_BUILD_CACHE_PATH=
-unset PYTHON_BUILD_ARIA2_OPTS
+export PYTHON_BUILD_ARIA2_OPTS=
 
 
 @test "package URL without checksum" {
diff --git a/plugins/python-build/test/mirror.bats b/plugins/python-build/test/mirror.bats
index fbffaf7c..ddc009dd 100644
--- a/plugins/python-build/test/mirror.bats
+++ b/plugins/python-build/test/mirror.bats
@@ -4,7 +4,7 @@ load test_helper
 export PYTHON_BUILD_SKIP_MIRROR=
 export PYTHON_BUILD_CACHE_PATH=
 export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
-unset PYTHON_BUILD_ARIA2_OPTS
+export PYTHON_BUILD_ARIA2_OPTS=
 
 
 @test "package URL without checksum bypasses mirror" {