diff --git a/include/CLI/impl/Option_inl.hpp b/include/CLI/impl/Option_inl.hpp
index ae78a2630..b37be4021 100644
--- a/include/CLI/impl/Option_inl.hpp
+++ b/include/CLI/impl/Option_inl.hpp
@@ -668,7 +668,7 @@ CLI11_INLINE int Option::_add_result(std::string &&result, std::vector<std::stri
             // this is an escape clause for odd strings
             std::string nstrs{'['};
             bool duplicated{true};
-            for(int ii = 2; ii < result.size() - 2; ii += 2) {
+            for(std::size_t ii = 2; ii < result.size() - 2; ii += 2) {
                 if(result[ii] == result[ii + 1]) {
                     nstrs.push_back(result[ii]);
                 } else {
@@ -677,6 +677,7 @@ CLI11_INLINE int Option::_add_result(std::string &&result, std::vector<std::stri
                 }
             }
             if(duplicated) {
+                nstrs.push_back(']');
                 res.push_back(std::move(nstrs));
                 ++result_count;
                 return result_count;
diff --git a/tests/OptionTypeTest.cpp b/tests/OptionTypeTest.cpp
index 09dfa1d2f..d237831ae 100644
--- a/tests/OptionTypeTest.cpp
+++ b/tests/OptionTypeTest.cpp
@@ -1225,6 +1225,21 @@ TEST_CASE_METHOD(TApp, "vectorSingleArg", "[optiontype]") {
     CHECK("4" == extra);
 }
 
+TEST_CASE_METHOD(TApp, "vectorEmptyArg", "[optiontype]") {
+
+    std::vector<std::string> cv{ "test" };
+    app.add_option("-c", cv);
+    args = { "-c","test1", "[]"};
+
+    run();
+    CHECK(cv.size()==1);
+    args = { "-c","test1", "[[]]"};
+
+    run();
+    CHECK(cv.size()==2);
+    CHECK(cv[1]=="[]");
+}
+
 TEST_CASE_METHOD(TApp, "vectorDoubleArg", "[optiontype]") {
 
     std::vector<std::pair<int, std::string>> cv;
diff --git a/tests/fuzzFail/round_trip_custom3 b/tests/fuzzFail/round_trip_custom3
new file mode 100644
index 000000000..e7991992d
Binary files /dev/null and b/tests/fuzzFail/round_trip_custom3 differ