diff --git a/cpp/include/raft/neighbors/detail/refine.cuh b/cpp/include/raft/neighbors/detail/refine.cuh
index 2dfaa5a5cb..7d3779c89e 100644
--- a/cpp/include/raft/neighbors/detail/refine.cuh
+++ b/cpp/include/raft/neighbors/detail/refine.cuh
@@ -141,7 +141,7 @@ typedef struct {
   float distance;
 } struct_for_refinement;
 
-int _postprocessing_qsort_compare(const void* v1, const void* v2)
+inline int _postprocessing_qsort_compare(const void* v1, const void* v2)
 {
   // sort in ascending order
   if (((struct_for_refinement*)v1)->distance > ((struct_for_refinement*)v2)->distance) {