diff --git a/include/GooseEYE/GooseEYE.h b/include/GooseEYE/GooseEYE.h
index ba207944..872759a6 100644
--- a/include/GooseEYE/GooseEYE.h
+++ b/include/GooseEYE/GooseEYE.h
@@ -732,8 +732,15 @@ class ClusterLabeller {
     {
 #ifdef GOOSEEYE_ENABLE_ASSERT
         size_t n = m_label.size();
-        GOOSEEYE_ASSERT(
-            !std::any_of(begin, end, [n](size_t i) { return i < 0 || i >= n; }), std::out_of_range);
+        if constexpr (std::is_signed_v<T::value_type>) {
+            GOOSEEYE_ASSERT(
+                !std::any_of(begin, end, [n](size_t i) { return i >= n; }), std::out_of_range);
+        }
+        else {
+            GOOSEEYE_ASSERT(
+                !std::any_of(begin, end, [n](size_t i) { return i < 0 || i >= n; }),
+                std::out_of_range);
+        }
 #endif
 
         for (auto it = begin; it != end; ++it) {
diff --git a/include/GooseEYE/config.h b/include/GooseEYE/config.h
index 2e7e42b5..1f1a4c21 100644
--- a/include/GooseEYE/config.h
+++ b/include/GooseEYE/config.h
@@ -27,6 +27,7 @@
 #include <memory>
 #include <numeric>
 #include <string>
+#include <type_traits>
 #include <vector>
 
 #include <xtensor/xadapt.hpp>