diff --git a/js/src/gc/GCRuntime.h b/js/src/gc/GCRuntime.h
index 1e4b4212447..6c666f17ec0 100644
--- a/js/src/gc/GCRuntime.h
+++ b/js/src/gc/GCRuntime.h
@@ -1037,8 +1037,16 @@ class GCRuntime
     };
     GrayBufferState grayBufferState;
     bool hasBufferedGrayRoots() const { return grayBufferState == GrayBufferState::Okay; }
+
+    // Clear each zone's gray buffers, but do not change the current state.
     void resetBufferedGrayRoots() const;
 
+    // Reset the gray buffering state to Unused.
+    void clearBufferedGrayRoots() {
+        grayBufferState = GrayBufferState::Unused;
+        resetBufferedGrayRoots();
+    }
+
     /*
      * The gray bits can become invalid if UnmarkGray overflows the stack. A
      * full GC will reset this bit, since it fills in all the gray bits.
diff --git a/js/src/gc/Tracer.cpp b/js/src/gc/Tracer.cpp
index ffa699d984f..c8f64cfc1d2 100644
--- a/js/src/gc/Tracer.cpp
+++ b/js/src/gc/Tracer.cpp
@@ -554,9 +554,6 @@ GCMarker::stop()
 
     /* Free non-ballast stack memory. */
     stack.reset();
-
-    runtime()->gc.resetBufferedGrayRoots();
-    runtime()->gc.grayBufferState = GCRuntime::GrayBufferState::Unused;
 }
 
 void
@@ -650,6 +647,8 @@ GCMarker::checkZone(void *p)
 void
 GCRuntime::resetBufferedGrayRoots() const
 {
+    MOZ_ASSERT(grayBufferState != GrayBufferState::Okay,
+               "Do not clear the gray buffers unless we are Failed or becoming Unused");
     for (GCZonesIter zone(rt); !zone.done(); zone.next())
         zone->gcGrayRoots.clearAndFree();
 }
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index 946002c1050..486a9dd0e78 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -5373,6 +5373,7 @@ GCRuntime::finishCollection(JS::gcreason::Reason reason)
 {
     MOZ_ASSERT(marker.isDrained());
     marker.stop();
+    clearBufferedGrayRoots();
 
     uint64_t currentTime = PRMJ_Now();
     schedulingState.updateHighFrequencyMode(lastGCTime, currentTime, tunables);
@@ -5496,6 +5497,7 @@ GCRuntime::resetIncrementalGC(const char *reason)
 
         marker.reset();
         marker.stop();
+        clearBufferedGrayRoots();
 
         for (GCCompartmentsIter c(rt); !c.done(); c.next())
             ResetGrayList(c);