diff --git a/ci-automation/vendor_test.sh b/ci-automation/vendor_test.sh
index 77fbd7b4f3..443add5821 100644
--- a/ci-automation/vendor_test.sh
+++ b/ci-automation/vendor_test.sh
@@ -155,6 +155,9 @@ function filter_prefixed_tests() {
     local -n results="${var_name}"
     local name
     local stripped_name
+    # clear the array, so it will contain results of current filtering
+    # only
+    results=()
     for name; do
         stripped_name="${name#extra-test.\[${prefix}\].}"
         if [[ "${stripped_name}" != "${name}" ]]; then
@@ -181,6 +184,9 @@ function filter_out_prefixed_tests() {
     local var_name="${1}"; shift
     local -n results="${var_name}"
     local name
+    # clear the array, so it will contain results of current filtering
+    # only
+    results=()
     for name; do
         if [[ "${name#extra-test.}" = "${name}" ]]; then
             results+=( "${name}" )