diff --git a/interop/src/cpp/DeserializerBase.h b/interop/src/cpp/DeserializerBase.h
index 219dcfbe274ab7e2b5adce118c5297f315605455..87fe3fc392bb6d037735247552eabcfecebf361e 100644
--- a/interop/src/cpp/DeserializerBase.h
+++ b/interop/src/cpp/DeserializerBase.h
@@ -563,12 +563,19 @@ inline void WriteToString(std::string *result, InteropUInt32 value)
 template <>
 inline void WriteToString(std::string *result, InteropFloat32 value)
 {
+#if (defined(__MAC_OS_X_VERSION_MAX_ALLOWED) && (__MAC_OS_X_VERSION_MAX_ALLOWED < 130300L))
+  // to_chars() is not available on older macOS.
+  char buf[20];
+  snprintf(buf, sizeof buf, "%f", value);
+  result->append(buf);
+#else
   std::string storage;
   storage.resize(20);
   // We use to_chars() to avoid locale issues.
   auto rc = std::to_chars(storage.data(), storage.data() + storage.size(), value);
   storage.resize(rc.ptr - storage.data());
   result->append(storage);
+#endif
 }
 template <>
 inline void WriteToString(std::string* result, const InteropBuffer* value) {