diff --git a/packages/logging/src/log.js b/packages/logging/src/log.js
index e20f4634052..760796ca6e6 100644
--- a/packages/logging/src/log.js
+++ b/packages/logging/src/log.js
@@ -118,10 +118,12 @@ util.inherits(Log, commonGrpc.ServiceObject);
  */
 Log.assignSeverityToEntries_ = function(entries, severity) {
   return arrify(entries).map(function(entry) {
-    return extend(true, new Entry(), entry, {
-      metadata: {
-        severity: severity
-      }
+    var metadata = extend(true, {}, entry.metadata, {
+      severity: severity
+    });
+
+    return extend(new Entry(), entry, {
+      metadata: metadata
     });
   });
 };
diff --git a/packages/logging/test/log.js b/packages/logging/test/log.js
index 274bac2920f..45c7e0b39c5 100644
--- a/packages/logging/test/log.js
+++ b/packages/logging/test/log.js
@@ -142,9 +142,13 @@ describe('Log', function() {
   });
 
   describe('assignSeverityToEntries_', function() {
+    var circular = {};
+    circular.circular = circular;
+
     var ENTRIES = [
       { data: { a: 'b' } },
-      { data: { c: 'd' } }
+      { data: { c: 'd' } },
+      { data: { e: circular }}
     ];
 
     var SEVERITY = 'severity';
@@ -164,6 +168,7 @@ describe('Log', function() {
           .map(prop('metadata'))
           .map(prop('severity')),
         [
+          SEVERITY,
           SEVERITY,
           SEVERITY
         ]