diff --git a/.github/workflows/build-and-test-rh.yml b/.github/workflows/build-and-test-rh.yml
index bb82d29..e2df65d 100644
--- a/.github/workflows/build-and-test-rh.yml
+++ b/.github/workflows/build-and-test-rh.yml
@@ -95,12 +95,21 @@ jobs:
         run:  sudo yum -y install findutils
 
       - name: Checkout shell test framework
+        if: matrix.image != 'centos:7'
         uses: actions/checkout@v4
         with:
           repository: kward/shunit2
           path: ${{github.workspace}}/tests/shunit2
           fetch-depth: 1
 
+      - name: Checkout shell test framework centos7
+        if: matrix.image == 'centos:7'
+        uses: actions/checkout@v3
+        with:
+          repository: kward/shunit2
+          path: ${{github.workspace}}/tests/shunit2
+          fetch-depth: 1
+
       - name: Run additional tests
         shell: bash
         run: tests/scripts/tests.sh
diff --git a/include/sexpp/sexp.h b/include/sexpp/sexp.h
index 9e2d1fd..de0d093 100644
--- a/include/sexpp/sexp.h
+++ b/include/sexpp/sexp.h
@@ -251,12 +251,14 @@ class SEXP_PUBLIC_SYMBOL sexp_string_t : public sexp_object_t {
 
 inline bool operator==(const sexp_string_t *left, const std::string &right) noexcept
 {
-    return memcmp(left->get_string().data(), right.c_str(), right.size()) == 0;
+    return left->get_string().size() == right.length() &&
+           memcmp(left->get_string().data(), right.c_str(), left->get_string().size()) == 0;
 }
 
 inline bool operator!=(const sexp_string_t *left, const std::string &right) noexcept
 {
-    return memcmp(left->get_string().data(), right.c_str(), right.size()) != 0;
+    return left->get_string().size() != right.length() ||
+           memcmp(left->get_string().data(), right.c_str(), left->get_string().size()) != 0;
 }
 
 /*