--- a/layout/tools/reftest/runreftest.py
+++ b/layout/tools/reftest/runreftest.py
@@ -562,18 +562,18 @@ class RefTest(object):
         debug_args = None
         if debuggerInfo:
             interactive = debuggerInfo.interactive
             debug_args = [debuggerInfo.path] + debuggerInfo.args
 
         def record_last_test(message):
             """Records the last test seen by this harness for the benefit of crash logging."""
             if message['action'] == 'test_start':
-                if isinstance(message['test'], tuple):
-                    self.lastTestSeen = message['test'][0]
+                if " " in message['test']:
+                    self.lastTestSeen = message['test'].split(" ")[0]
                 else:
                     self.lastTestSeen = message['test']
 
         self.log.add_handler(record_last_test)
 
         outputHandler = OutputHandler(self.log, options.utilityPath, symbolsPath=symbolsPath)
 
         kp_kwargs = {

--- a/testing/modules/StructuredLog.jsm
+++ b/testing/modules/StructuredLog.jsm
@@ -29,30 +29,30 @@ this.StructuredLogger = function(name, d
   this._mutatorFuns = mutators;
 }
 
 /**
  * Log functions producing messages in the format specified by mozlog
  */
 StructuredLogger.prototype = {
   testStart: function (test) {
-    var data = {test: test};
+    var data = {test: this._testId(test)};
     this._logData("test_start", data);
   },
 
   testStatus: function (test, subtest, status, expected="PASS",
                         message=null, stack=null, extra=null) {
 
     if (subtest === null || subtest === undefined) {
       // Fix for assertions that don't pass in a name
       subtest = "undefined assertion name";
     }
 
     var data = {
-      test: test,
+      test: this._testId(test),
       subtest: subtest,
       status: status,
     };
 
     if (expected != status && status != "SKIP") {
       data.expected = expected;
     }
     if (message !== null) {
@@ -64,17 +64,17 @@ StructuredLogger.prototype = {
     if (extra !== null) {
       data.extra = extra;
     }
 
     this._logData("test_status", data);
   },
 
   testEnd: function (test, status, expected="OK", message=null, stack=null, extra=null) {
-    var data = {test: test, status: status};
+    var data = {test: this._testId(test), status: status};
 
     if (expected != status && status != "SKIP") {
       data.expected = expected;
     }
     if (message !== null) {
       data.message = String(message);
     }
     if (stack !== null) {
@@ -83,17 +83,17 @@ StructuredLogger.prototype = {
     if (extra !== null) {
       data.extra = extra;
     }
 
     this._logData("test_end", data);
   },
 
   suiteStart: function (tests, runinfo=null, versioninfo=null, deviceinfo=null, extra=null) {
-    var data = {tests: tests};
+    var data = {tests: tests.map(x => this._testId(x))};
     if (runinfo !== null) {
       data.runinfo = runinfo;
     }
 
     if (versioninfo !== null) {
       data.versioninfo = versioninfo;
     }
 
@@ -181,17 +181,24 @@ StructuredLogger.prototype = {
       allData[field] = data[field];
     }
 
     for (var fun of this._mutatorFuns) {
       fun(allData);
     }
 
     this._dumpFun(allData);
-  }
+  },
+
+  _testId: function(test) {
+    if (Array.isArray(test)) {
+      return test.join(" ");
+    }
+    return test;
+  },
 };
 
 
 /**
  * StructuredFormatter: Formatter class turning structured messages
  * into human-readable messages.
  */
 this.StructuredFormatter = function() {