diff --git a/image_analysis/indexing/IndexerThreadPool.cpp b/image_analysis/indexing/IndexerThreadPool.cpp
index ea4150583..d849acb01 100644
--- a/image_analysis/indexing/IndexerThreadPool.cpp
+++ b/image_analysis/indexing/IndexerThreadPool.cpp
@@ -59,6 +59,7 @@ FFTPlanReuse::~FFTPlanReuse() = default;
 FFTIndexerReuse::FFTIndexerReuse() = default;
 FFTIndexerReuse::~FFTIndexerReuse() = default;
 void KeepFFTIndexers(const IndexingSettings &, int) {}
+void ReleaseKeptFFTIndexers() {}
 #endif
 
 #ifdef JFJOCH_USE_CUDA
@@ -152,6 +153,18 @@ static std::unique_ptr<Indexer> MakeFFTIndexerGPU(const IndexingSettings &settin
     return std::make_unique<FFTIndexerGPU>(settings);
 }
 
+void ReleaseKeptFFTIndexers() {
+    std::map<FFTIndexerKey, std::vector<std::unique_ptr<Indexer>>> idle;
+    {
+        std::lock_guard lock(kept_fft_indexers().m);
+        idle.swap(kept_fft_indexers().idle);
+    }
+    for (auto &[key, list] : idle) {
+        ScopedGpuPin pin(std::get<0>(key));
+        list.clear();
+    }
+}
+
 void KeepFFTIndexers(const IndexingSettings &settings, int count) {
     if (get_gpu_count() == 0)
         return;
diff --git a/image_analysis/indexing/IndexerThreadPool.h b/image_analysis/indexing/IndexerThreadPool.h
index 023f6971d..1a61be816 100644
--- a/image_analysis/indexing/IndexerThreadPool.h
+++ b/image_analysis/indexing/IndexerThreadPool.h
@@ -74,6 +74,9 @@ public:
 // destroyed). Nothing without a GPU.
 void KeepFFTIndexers(const IndexingSettings &settings, int count);
 
+// Destroys the kept FFT indexers that no pool is using: a settings change leaves them keyed on the old settings.
+void ReleaseKeptFFTIndexers();
+
 class IndexerThread {
     struct TaskInput {
         const DiffractionExperiment &experiment;
diff --git a/receiver/JFJochReceiverService.cpp b/receiver/JFJochReceiverService.cpp
index d3f8f0fac..868369b08 100644
--- a/receiver/JFJochReceiverService.cpp
+++ b/receiver/JFJochReceiverService.cpp
@@ -389,6 +389,7 @@ JFJochReceiverService &JFJochReceiverService::Indexing(const IndexingSettings &i
 
         logger.Info("Resetting indexing thread pool");
         indexer_thread_pool.reset();
+        ReleaseKeptFFTIndexers();
 
         if (input.GetAlgorithm() != IndexingAlgorithmEnum::None) {
             logger.Info("Creating indexing thread pool...");
diff --git a/tests/CUDAMemHelpersTest.cpp b/tests/CUDAMemHelpersTest.cpp
index 6f5cf08fd..a01e008e9 100644
--- a/tests/CUDAMemHelpersTest.cpp
+++ b/tests/CUDAMemHelpersTest.cpp
@@ -443,6 +443,10 @@ TEST_CASE("IndexerThreadPool_FFTIndexerKeptAcrossPools", "[CUDAMemHelpers]") {
             CHECK(r.lattice.size() == fresh.lattice.size());
         }
         CHECK(pooled() == kept);
+
+        // A settings change in the broker: the kept indexers go while the reuse scope lives on
+        ReleaseKeptFFTIndexers();
+        CHECK(pooled() <= before + (uint64_t(16) << 20));
     }
     CHECK(pooled() <= before + (uint64_t(16) << 20));
     for (int d = 0; d < get_gpu_count(); d++) {