diff --git a/CPP/7zip/Compress/BrotliDecoder.cpp b/CPP/7zip/Compress/BrotliDecoder.cpp
index 5027c089..910ec4f7 100644
--- a/CPP/7zip/Compress/BrotliDecoder.cpp
+++ b/CPP/7zip/Compress/BrotliDecoder.cpp
@@ -100,6 +100,10 @@ STDMETHODIMP CDecoder::SetNumberOfThreads(UInt32 numThreads)
   const UInt32 kNumThreadsMax = BROTLIMT_THREAD_MAX;
   if (numThreads < 0) numThreads = 0;
   if (numThreads > kNumThreadsMax) numThreads = kNumThreadsMax;
+  // if single-threaded, retain artificial number set in BrotliHandler (always prefer .br format):
+  if (_numThreads == 0 && numThreads == 1) {
+    numThreads = 0;
+  }
   _numThreads = numThreads;
   return S_OK;
 }
diff --git a/CPP/7zip/Compress/BrotliEncoder.cpp b/CPP/7zip/Compress/BrotliEncoder.cpp
index b1dcb613..b44fc582 100644
--- a/CPP/7zip/Compress/BrotliEncoder.cpp
+++ b/CPP/7zip/Compress/BrotliEncoder.cpp
@@ -156,6 +156,10 @@ STDMETHODIMP CEncoder::SetNumberOfThreads(UInt32 numThreads)
   const UInt32 kNumThreadsMax = BROTLIMT_THREAD_MAX;
   if (numThreads < 0) numThreads = 0;
   if (numThreads > kNumThreadsMax) numThreads = kNumThreadsMax;
+  // if single-threaded, retain artificial number set in BrotliHandler (always prefer .br format):
+  if (_numThreads == 0 && numThreads == 1) {
+    numThreads = 0;
+  }
   _numThreads = numThreads;
   return S_OK;
 }