diff --git a/src/mongo/crypto/fle_tokens.cpp b/src/mongo/crypto/fle_tokens.cpp
index d6a09e660cb..afd9bd9c82a 100644
--- a/src/mongo/crypto/fle_tokens.cpp
+++ b/src/mongo/crypto/fle_tokens.cpp
@@ -47,13 +47,13 @@ typedef _mongocrypt_crypto_t mongocrypt_crypto_t;
 
 namespace mongo {
 
-auto kEmptyPrfBlock = MongoCryptBuffer::copy(ConstDataRange(PrfBlock{}));
+const auto kEmptyPrfBlock = MongoCryptBuffer::copy(ConstDataRange(PrfBlock{}));
 
 #define FLE_TOKEN_TYPE_MC(TokenType) mc_##TokenType##_t
 
 // Variadic arguments represent parameters for the token's ::deriveFrom function.
 #define FLE_TOKEN_CLASS_IMPL_BEGIN(TokenType, ...)                                                \
-    void TokenType::initializeFromBuffer(MongoCryptBuffer buffer) {                               \
+    void TokenType::initializeFromBuffer(const MongoCryptBuffer& buffer) {                        \
         _token = mc_##TokenType##_new_from_buffer_copy(buffer.get());                             \
     }                                                                                             \
                                                                                                   \
diff --git a/src/mongo/crypto/fle_tokens.h b/src/mongo/crypto/fle_tokens.h
index 0e0904188db..c303c32a728 100644
--- a/src/mongo/crypto/fle_tokens.h
+++ b/src/mongo/crypto/fle_tokens.h
@@ -158,7 +158,7 @@ public:
     private:                                                                   \
         FLE_TOKEN_TYPE_MC(TokenType) * _token;                                 \
                                                                                \
-        void initializeFromBuffer(MongoCryptBuffer buffer);                    \
+        void initializeFromBuffer(const MongoCryptBuffer& buffer);             \
     };                                                                         \
     }