diff --git a/include/dwarfs/nilsimsa.h b/include/dwarfs/nilsimsa.h
index 541944e3..a1a440bb 100644
--- a/include/dwarfs/nilsimsa.h
+++ b/include/dwarfs/nilsimsa.h
@@ -27,19 +27,8 @@
 #include <span>
 #include <type_traits>
 
-#include <folly/lang/Bits.h>
-
 #include "dwarfs/compiler.h"
 
-#define DWARFS_NILSIMSA_SIMILARITY(r, a, b)                                    \
-  do {                                                                         \
-    int bits = 0;                                                              \
-    for (int i = 0; i < 4; ++i) {                                              \
-      bits += folly::popcount(a[i] ^ b[i]);                                    \
-    }                                                                          \
-    r 255 - bits;                                                              \
-  } while (false)
-
 namespace dwarfs {
 
 class nilsimsa {
@@ -52,15 +41,6 @@ class nilsimsa {
   void update(uint8_t const* data, size_t size);
   void finalize(hash_type& hash) const;
 
-#ifdef DWARFS_MULTIVERSIONING
-  __attribute__((target("popcnt"))) static int
-  similarity(uint64_t const* a, uint64_t const* b);
-
-  __attribute__((target("default")))
-#endif
-  static int
-  similarity(uint64_t const* a, uint64_t const* b);
-
   void operator()(std::span<uint8_t const> data) {
     update(data.data(), data.size());
   }
diff --git a/src/dwarfs/nilsimsa.cpp b/src/dwarfs/nilsimsa.cpp
index 9d795a04..b169d7ee 100644
--- a/src/dwarfs/nilsimsa.cpp
+++ b/src/dwarfs/nilsimsa.cpp
@@ -192,19 +192,4 @@ void nilsimsa::update(uint8_t const* data, size_t size) {
 
 void nilsimsa::finalize(hash_type& hash) const { impl_->finalize(hash); }
 
-#ifdef DWARFS_MULTIVERSIONING
-__attribute__((target("popcnt"))) int
-nilsimsa::similarity(uint64_t const* a, uint64_t const* b) {
-  DWARFS_NILSIMSA_SIMILARITY(return, a, b);
-}
-
-__attribute__((target("default")))
-#endif
-int nilsimsa::similarity(uint64_t const* a, uint64_t const* b) {
-  DWARFS_NILSIMSA_SIMILARITY(return, a, b);
-}
-
-static_assert(std::is_same_v<unsigned long, uint64_t> ||
-              std::is_same_v<unsigned long long, uint64_t>);
-
 } // namespace dwarfs