diff --git a/tests/cpp/format/json.cc b/tests/cpp/format/json.cc
index 9c16261d..a88b3279 100644
--- a/tests/cpp/format/json.cc
+++ b/tests/cpp/format/json.cc
@@ -122,10 +122,16 @@ TEST(real) {
 }
 
 TEST(string) {
+  // Helper function that concatenates all arguments into one string.
+  auto concat = [](auto... args) {
+    std::string result;
+    (result += ... += args);
+    return result;
+  };
   CHECK_EQUAL(to_v1("foo"sv), R"_({"@data-type":"string","data":"foo"})_");
   CHECK_EQUAL(to_v1("foo\nbar"sv),
               R"_({"@data-type":"string","data":"foo\nbar"})_");
-  CHECK_EQUAL(to_v1("foo\n\"bar"sv),
+  CHECK_EQUAL(to_v1(concat("foo\n", '"', "bar")), // concat: workaround for MSVC
               R"_({"@data-type":"string","data":"foo\n\"bar"})_");
   CHECK_EQUAL(to_v1(data{"foo"s}), R"_({"@data-type":"string","data":"foo"})_");
   CHECK_EQUAL(to_v1(data{"foo\nbar"s}),