diff --git a/js/src/gc/Allocator.cpp b/js/src/gc/Allocator.cpp
index be9924db02..395c39adaa 100644
--- a/js/src/gc/Allocator.cpp
+++ b/js/src/gc/Allocator.cpp
@@ -215,18 +215,6 @@ js::Allocate(ExclusiveContext* cx)
     AllocKind kind = MapTypeToFinalizeKind<T>::kind;
     size_t thingSize = sizeof(T);
 
-    // === ADD DETAILED DIAGNOSTIC OUTPUT HERE ===
-    size_t arenaSize = Arena::thingSize(kind);
-    
-    fprintf(stderr, "\n=== GC Allocation Debug ===\n");
-    fprintf(stderr, "Type name: %s\n", typeid(T).name());
-    fprintf(stderr, "sizeof(T): %zu bytes\n", thingSize);
-    fprintf(stderr, "Arena::thingSize(kind): %zu bytes\n", arenaSize);
-    fprintf(stderr, "CellAlignBytes: %zu bytes\n", CellAlignBytes);
-    fprintf(stderr, "Match: %s\n", (thingSize == arenaSize) ? "YES" : "NO - MISMATCH!");
-    fprintf(stderr, "Size difference: %zd bytes\n", (size_t)thingSize - (size_t)arenaSize);
-    fprintf(stderr, "========================\n\n");
-
     MOZ_ASSERT(thingSize == Arena::thingSize(kind));
 
     if (cx->isJSContext()) {
diff --git a/js/src/gc/GCInternals.h b/js/src/gc/GCInternals.h
index 7d2340e36a..0997401deb 100644
--- a/js/src/gc/GCInternals.h
+++ b/js/src/gc/GCInternals.h
@@ -147,6 +147,22 @@ struct MOZ_RAII AutoAssertNoNurseryAlloc
 #endif
 };
 
+// Note that this class does not suppress buffer allocation/reallocation in the
+// nursery, only Cells themselves.
+class MOZ_RAII AutoSuppressNurseryCellAlloc
+{
+    JSContext* cx_;
+
+  public:
+
+    explicit AutoSuppressNurseryCellAlloc(JSContext* cx) : cx_(cx) {
+        cx_->nurserySuppressions_++;
+    }
+    ~AutoSuppressNurseryCellAlloc() {
+        cx_->nurserySuppressions_--;
+    }
+};
+
 /*
  * There are a couple of classes here that serve mostly as "tokens" indicating
  * that a condition holds. Some functions force the caller to possess such a
diff --git a/js/src/gc/Marking.cpp b/js/src/gc/Marking.cpp
index 03a50b89e8..21abe014b0 100644
--- a/js/src/gc/Marking.cpp
+++ b/js/src/gc/Marking.cpp
@@ -1774,7 +1774,9 @@ GCMarker::processMarkStackTop(SliceBudget& budget)
         } else if (v.isBigInt()) {
             traverseEdge(obj, v.toBigInt());
         } else if (v.isPrivateGCThing()) {
-            traverseEdge(obj, v.toGCCellPtr());
+            // v.toGCCellPtr cannot be inlined, so construct one manually.
+            Cell* cell = v.toGCThing();
+            traverseEdge(obj, JS::GCCellPtr(cell, cell->getTraceKind()));
         }
     }
     return;
@@ -2713,6 +2715,7 @@ inline void
 js::TenuringTracer::traceSlots(JS::Value* vp, uint32_t nslots)
 {
     traceSlots(vp, vp + nslots);
+}
 
 void
 js::TenuringTracer::traceString(JSString* str)
diff --git a/js/src/gc/Nursery.cpp b/js/src/gc/Nursery.cpp
index 4b0f8c0702..2084f16290 100644
--- a/js/src/gc/Nursery.cpp
+++ b/js/src/gc/Nursery.cpp
@@ -840,9 +840,9 @@ js::Nursery::doCollection(JS::gcreason::Reason reason,
     }
     endProfile(ProfileKey::MarkDebugger);
 
-    maybeStartProfile(ProfileKey::SweepCaches);
+    startProfile(ProfileKey::SweepCaches);
     rt->gc.purgeRuntimeForMinorGC();
-    maybeEndProfile(ProfileKey::SweepCaches);
+    endProfile(ProfileKey::SweepCaches);
 
     // Most of the work is done here. This loop iterates over objects that have
     // been moved to the major heap. If these objects have any outgoing pointers
diff --git a/js/src/gc/Verifier.cpp b/js/src/gc/Verifier.cpp
index 41839bf47e..60e933ad8b 100644
--- a/js/src/gc/Verifier.cpp
+++ b/js/src/gc/Verifier.cpp
@@ -540,7 +540,7 @@ CheckHeapTracer::onChild(const JS::GCCellPtr& thing)
     else
         zone = cell->asTenured().zone();
 
-    if (zone->group() && zone->group()->usedByHelperThread)
+    if (zone->group() && zone->group()->usedByHelperThread())
         return;
     }
 
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index d6d9e091c6..9fdb9bc45b 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -4782,7 +4782,7 @@ NextIncomingCrossCompartmentPointer(JSObject* prev, bool unlink)
 }
 
 void
-js::DelayCrossCompartmentGrayMarking(JSObject* src)
+js::gc::DelayCrossCompartmentGrayMarking(JSObject* src)
 {
     MOZ_ASSERT(IsGrayListObject(src));