diff --git a/include/xgboost/linalg.h b/include/xgboost/linalg.h
index 65e9de6ba..4ca5b9f7e 100644
--- a/include/xgboost/linalg.h
+++ b/include/xgboost/linalg.h
@@ -150,7 +150,7 @@ inline LINALG_HD int Popc(uint64_t v) {
   return __popcll(v);
 #elif defined(__GNUC__) || defined(__clang__)
   return __builtin_popcountll(v);
-#elif defined(_MSC_VER) && _defined(_M_X64)
+#elif defined(_MSC_VER) && defined(_M_X64)
   return __popcnt64(v);
 #else
   return NativePopc(v);