diff --git a/faiss/IndexIVFPQFastScan.cpp b/faiss/IndexIVFPQFastScan.cpp
index 9b9c05783..bcfdf41c1 100644
--- a/faiss/IndexIVFPQFastScan.cpp
+++ b/faiss/IndexIVFPQFastScan.cpp
@@ -319,7 +319,8 @@ namespace {
 
 struct IVFPQFastScanScanner : InvertedListScanner {
     using InvertedListScanner::scan_codes;
-    static constexpr int impl = 10; // based on search_implem_10
+    [[maybe_unused]] static constexpr int impl =
+            10;                     // based on search_implem_10
     static constexpr size_t nq = 1; // 1 query at a time.
     const IndexIVFPQFastScan& index;
     AlignedTable<uint8_t> dis_tables;
diff --git a/faiss/IndexIVFRaBitQFastScan.cpp b/faiss/IndexIVFRaBitQFastScan.cpp
index 752df158c..b3f7c1cb5 100644
--- a/faiss/IndexIVFRaBitQFastScan.cpp
+++ b/faiss/IndexIVFRaBitQFastScan.cpp
@@ -573,7 +573,7 @@ namespace {
 /// Provides IVF scanner interface using FastScan's SIMD batch processing.
 struct IVFRaBitQFastScanScanner : InvertedListScanner {
     using InvertedListScanner::scan_codes;
-    static constexpr int impl = 10;
+    [[maybe_unused]] static constexpr int impl = 10;
     static constexpr size_t nq = 1;
 
     const IndexIVFRaBitQFastScan& index;