diff --git a/src/pbrt/wavefront/integrator.h b/src/pbrt/wavefront/integrator.h
index cbb8d9116a08fba6a61b03ec3f24eb1c26eddd2d..e85312ad66036b01d20bc839f5165553ab97f6fb 100644
--- a/src/pbrt/wavefront/integrator.h
+++ b/src/pbrt/wavefront/integrator.h
@@ -111,7 +111,7 @@ class WavefrontPathIntegrator {
     void Do(const char *description, F &&func) {
         if (Options->useGPU)
 #ifdef PBRT_BUILD_GPU_RENDERER
-            GPUParallelFor(description, 1, [=] PBRT_GPU(int) { func(); });
+            GPUParallelFor(description, 1, [=] PBRT_GPU(int) mutable { func(); });
 #else
             LOG_FATAL("Options->useGPU was set without PBRT_BUILD_GPU_RENDERER enabled");
 #endif
diff --git a/src/pbrt/wavefront/workqueue.h b/src/pbrt/wavefront/workqueue.h
index 688160708e4843bd4d499ad84c07b1d70403189c..2f0827e4d4077cdc5ebdffbc5a68e65dc4e6139d 100644
--- a/src/pbrt/wavefront/workqueue.h
+++ b/src/pbrt/wavefront/workqueue.h
@@ -121,7 +121,7 @@ void ForAllQueued(const char *desc, const WorkQueue<WorkItem> *q, int maxQueued,
     if (Options->useGPU) {
         // Launch GPU threads to process _q_ using _func_
 #ifdef PBRT_BUILD_GPU_RENDERER
-        GPUParallelFor(desc, maxQueued, [=] PBRT_GPU(int index) {
+        GPUParallelFor(desc, maxQueued, [=] PBRT_GPU(int index) mutable {
             if (index >= q->Size())
                 return;
             func((*q)[index]);