diff --git a/include/sdbusplus/utility/dedup_variant.hpp b/include/sdbusplus/utility/dedup_variant.hpp
index bfffd20f..786f7ef4 100644
--- a/include/sdbusplus/utility/dedup_variant.hpp
+++ b/include/sdbusplus/utility/dedup_variant.hpp
@@ -25,6 +25,7 @@ template <typename T, typename... Unused>
 struct dedup_variant
 {
     using type = T;
+    static_assert(sizeof...(Unused) == 0);
 };
 
 /** Find the deduplicated variant type.
diff --git a/include/sdbusplus/utility/merge_variants.hpp b/include/sdbusplus/utility/merge_variants.hpp
index 89c55711..70796821 100644
--- a/include/sdbusplus/utility/merge_variants.hpp
+++ b/include/sdbusplus/utility/merge_variants.hpp
@@ -26,6 +26,7 @@ template <typename T, typename... Unused>
 struct merge_variants
 {
     using type = T;
+    static_assert(sizeof...(Unused) == 0);
 };
 
 /** Compute the merged variant type.