diff --git a/connections/clients/windows/dart/core_adapter_dart.cc b/connections/clients/windows/dart/core_adapter_dart.cc
index 11a4eff6..9697ed38 100644
--- a/connections/clients/windows/dart/core_adapter_dart.cc
+++ b/connections/clients/windows/dart/core_adapter_dart.cc
@@ -519,11 +519,15 @@ std::string GetPayloadPath(location::nearby::PayloadId payload_id) {
                    // process is responsible for freeing this resource once it
                    // is no longer needed by calling CoTaskMemFree, whether
                    // SHGetKnownFolderPath succeeds or not.
-
-  char *fullpathUTF8 = new char((wcslen(basePath) + 1) * sizeof(char));
-  wcstombs(fullpathUTF8, basePath, (wcslen(basePath) + 1) * sizeof(char));
-
-  return absl::StrCat(fullpathUTF8, "\\", payload_id);
+  size_t bufferSize;
+  wcstombs_s(&bufferSize, NULL, 0, basePath, 0);
+  char *fullpathUTF8 = new char[bufferSize + 1];
+  memset(fullpathUTF8, 0, bufferSize);
+  wcstombs_s(&bufferSize, fullpathUTF8, bufferSize, basePath, bufferSize - 1);
+  std::string fullPath = std::string(fullpathUTF8);
+  auto retval = absl::StrCat(fullPath, "\\", payload_id);
+  delete[] fullpathUTF8;
+  return retval;
 }
 
 void SendPayloadDart(Core *pCore, const char *endpoint_id,