diff --git a/js/public/ProfilingFrameIterator.h b/js/public/ProfilingFrameIterator.h
index 37cd8658b686..cf6c565d81da 100644
--- a/js/public/ProfilingFrameIterator.h
+++ b/js/public/ProfilingFrameIterator.h
@@ -109,7 +109,7 @@ class JS_PUBLIC_API(ProfilingFrameIterator)
         void *returnAddress;
         void *activation;
         const char *label;
-        bool hasTrackedOptimizations;
+        bool mightHaveTrackedOptimizations;
     };
     uint32_t extractStack(Frame *frames, uint32_t offset, uint32_t end) const;
 
diff --git a/js/src/vm/Stack.cpp b/js/src/vm/Stack.cpp
index b247c51b1d8b..8f7fb194d969 100644
--- a/js/src/vm/Stack.cpp
+++ b/js/src/vm/Stack.cpp
@@ -1862,7 +1862,7 @@ JS::ProfilingFrameIterator::extractStack(Frame *frames, uint32_t offset, uint32_
         frames[offset].returnAddress = nullptr;
         frames[offset].activation = activation_;
         frames[offset].label = asmJSIter().label();
-        frames[offset].hasTrackedOptimizations = false;
+        frames[offset].mightHaveTrackedOptimizations = false;
         return 1;
     }
 
@@ -1898,21 +1898,16 @@ JS::ProfilingFrameIterator::extractStack(Frame *frames, uint32_t offset, uint32_
         frames[offset + i].returnAddress = returnAddr;
         frames[offset + i].activation = activation_;
         frames[offset + i].label = labels[i];
-        frames[offset + i].hasTrackedOptimizations = false;
+        frames[offset + i].mightHaveTrackedOptimizations = false;
     }
 
-    // Extract the index into the side table of optimization information and
-    // store it on the youngest frame. All inlined frames will have the same
-    // optimization information by virtue of sharing the JitcodeGlobalEntry,
-    // but such information is only interpretable on the youngest frame.
+    // A particular return address might have tracked optimizations only if
+    // there are any optimizations at all.
     //
-    // FIXMEshu: disabled until we can ensure the optimization info is live
-    // when we write out the JSON stream of the profile.
-    if (false && entry.hasTrackedOptimizations()) {
-        uint32_t dummy;
-        mozilla::Maybe<uint8_t> index = entry.trackedOptimizationIndexAtAddr(returnAddr, &dummy);
-        frames[offset].hasTrackedOptimizations = index.isSome();
-    }
+    // All inlined Ion frames will have the same optimization information by
+    // virtue of sharing the JitcodeGlobalEntry, but such information is only
+    // interpretable on the youngest frame.
+    frames[offset].mightHaveTrackedOptimizations = entry.hasTrackedOptimizations();
 
     return depth;
 }
diff --git a/tools/profiler/ProfileEntry.cpp b/tools/profiler/ProfileEntry.cpp
index da93db056013..c714472cc5bc 100644
--- a/tools/profiler/ProfileEntry.cpp
+++ b/tools/profiler/ProfileEntry.cpp
@@ -343,7 +343,7 @@ void UniqueJITOptimizations::stream(JSStreamWriter& b, JSRuntime* rt)
 }
 
 void ProfileBuffer::StreamSamplesToJSObject(JSStreamWriter& b, int aThreadId, JSRuntime* rt,
-                                            UniqueJITOptimizations &aUniqueOpts)
+                                            UniqueJITOptimizations& aUniqueOpts)
 {
   b.BeginArray();
 
@@ -468,7 +468,8 @@ void ProfileBuffer::StreamSamplesToJSObject(JSStreamWriter& b, int aThreadId, JS
                       }
                       readAheadPos = (framePos + incBy) % mEntrySize;
                       if (readAheadPos != mWritePos &&
-                          mEntries[readAheadPos].mTagName == 'J') {
+                          (mEntries[readAheadPos].mTagName == 'J' ||
+                           mEntries[readAheadPos].mTagName == 'O')) {
                         void* pc = mEntries[readAheadPos].mTagPtr;
 
                         // TODOshu: cannot stream tracked optimization info if
@@ -486,11 +487,16 @@ void ProfileBuffer::StreamSamplesToJSObject(JSStreamWriter& b, int aThreadId, JS
                           // Sampled JIT optimizations are deduplicated by
                           // aUniqueOpts to save space. Stream an index that
                           // references into the optimizations array.
-                          Maybe<unsigned> optsIndex = aUniqueOpts.getIndex(pc, rt);
-                          if (optsIndex.isSome()) {
-                            b.NameValue("optsIndex", optsIndex.value());
+                          bool mightHaveTrackedOpts = mEntries[readAheadPos].mTagName == 'O';
+                          if (mightHaveTrackedOpts) {
+                            Maybe<unsigned> optsIndex = aUniqueOpts.getIndex(pc, rt);
+                            if (optsIndex.isSome()) {
+                              b.NameValue("optsIndex", optsIndex.value());
+                            }
                           }
                         }
+
+                        incBy++;
                       }
                     b.EndObject();
                   }
diff --git a/tools/profiler/TableTicker.cpp b/tools/profiler/TableTicker.cpp
index 2d419a639930..9cec5dce6219 100644
--- a/tools/profiler/TableTicker.cpp
+++ b/tools/profiler/TableTicker.cpp
@@ -596,11 +596,16 @@ void mergeStacksIntoProfile(ThreadProfile& aProfile, TickSample* aSample, Native
     // Check to see if JS jit stack frame is top-most
     if (jsStackAddr > nativeStackAddr) {
       MOZ_ASSERT(jsIndex >= 0);
-      addDynamicTag(aProfile, 'c', jsFrames[jsIndex].label);
+      const JS::ProfilingFrameIterator::Frame& jsFrame = jsFrames[jsIndex];
+      addDynamicTag(aProfile, 'c', jsFrame.label);
 
-      // Stringifying optimization information is delayed until streaming
-      // time. To re-lookup the entry in the JitcodeGlobalTable, we need to
-      // store the JIT code address ('J') in the circular buffer.
+      // Stringifying optimization information and the JIT tier is delayed
+      // until streaming time. To re-lookup the entry in the
+      // JitcodeGlobalTable, we need to store the JIT code address in the
+      // circular buffer.
+      //
+      // Frames which may have optimization information are tagged by an 'O'
+      // entry. Otherwise they are tagged by a 'J' entry.
       //
       // Note that we cannot do this when we are sychronously sampling the
       // current thread; that is, when called from profiler_get_backtrace. The
@@ -611,12 +616,11 @@ void mergeStacksIntoProfile(ThreadProfile& aProfile, TickSample* aSample, Native
       // its JIT code. This means that if we inserted such 'J' entries into
       // the buffer, nsRefreshDriver would now be holding on to a backtrace
       // with stale JIT code return addresses.
-      MOZ_ASSERT_IF(jsFrames[jsIndex].hasTrackedOptimizations,
-                    jsFrames[jsIndex].kind == JS::ProfilingFrameIterator::Frame_Ion);
       if (!aSample->isSamplingCurrentThread &&
-          (jsFrames[jsIndex].kind == JS::ProfilingFrameIterator::Frame_Ion ||
-           jsFrames[jsIndex].kind == JS::ProfilingFrameIterator::Frame_Baseline)) {
-        aProfile.addTag(ProfileEntry('J', jsFrames[jsIndex].returnAddress));
+          (jsFrame.kind == JS::ProfilingFrameIterator::Frame_Ion ||
+           jsFrame.kind == JS::ProfilingFrameIterator::Frame_Baseline)) {
+        char entryTag = jsFrame.mightHaveTrackedOptimizations ? 'O' : 'J';
+        aProfile.addTag(ProfileEntry(entryTag, jsFrames[jsIndex].returnAddress));
       }
 
       jsIndex--;