diff --git a/src/dwarfs/nilsimsa.cpp b/src/dwarfs/nilsimsa.cpp
index 02a12880..cf88ea50 100644
--- a/src/dwarfs/nilsimsa.cpp
+++ b/src/dwarfs/nilsimsa.cpp
@@ -176,7 +176,7 @@ class nilsimsa::impl {
   }                                                                            \
   static_assert(true, "")
 
-#ifndef DWARFS_MULTIVERSIONING
+#ifdef DWARFS_MULTIVERSIONING
   __attribute__((target("avx"))) DWARFS_NILSIMSA_UPDATE_FAST_IMPL;
   __attribute__((target("default")))
 #endif