diff --git a/utils.cc b/utils.cc
index 62581f4..2bcc311 100644
--- a/utils.cc
+++ b/utils.cc
@@ -802,7 +802,7 @@
   return (b ? "true" : "false");
 }
 
-std::string ToString(DownloadSource source) {
+string ToString(DownloadSource source) {
   switch (source) {
     case kDownloadSourceHttpsServer: return "HttpsServer";
     case kDownloadSourceHttpServer:  return "HttpServer";
@@ -814,6 +814,19 @@
   return "Unknown";
 }
 
+string ToString(PayloadType payload_type) {
+  switch (payload_type) {
+    case kPayloadTypeDelta:      return "Delta";
+    case kPayloadTypeFull:       return "Full";
+    case kPayloadTypeForcedFull: return "ForcedFull";
+    case kNumPayloadTypes:       return "Unknown";
+    // Don't add a default case to let the compiler warn about newly added
+    // payload types which should be added here.
+  }
+
+  return "Unknown";
+}
+
 ErrorCode GetBaseErrorCode(ErrorCode code) {
   // Ignore the higher order bits in the code by applying the mask as
   // we want the enumerations to be in the small contiguous range