diff --git a/geom/sample.hpp b/geom/sample.hpp
index 41f1d6a0..c722a657 100644
--- a/geom/sample.hpp
+++ b/geom/sample.hpp
@@ -160,7 +160,7 @@ namespace util::geom {
                 // points is the greatest (while also being greater than the
                 // required minimum distance);
                 auto best_distance2 = std::numeric_limits<value_type>::lowest ();
-                size_t best_index;
+                size_t best_index = 0;
 
                 for (size_t i = 0; i < candidates.size (); ++i) {
                     auto const p = candidates[i];