diff --git a/headers/flat_hpp/flat_map.hpp b/headers/flat_hpp/flat_map.hpp
index cca641a..90306f9 100644
--- a/headers/flat_hpp/flat_map.hpp
+++ b/headers/flat_hpp/flat_map.hpp
@@ -135,6 +135,14 @@ namespace flat_hpp
             insert(ilist);
         }
 
+        flat_map(flat_map&& other, const Allocator& a)
+        : data_(std::move(other.data_), a)
+        , compare_(std::move(other.compare_)) {}
+
+        flat_map(const flat_map& other, const Allocator& a)
+        : data_(other.data_, a)
+        , compare_(other.compare_) {}
+
         flat_map(flat_map&& other) = default;
         flat_map(const flat_map& other) = default;
 
diff --git a/headers/flat_hpp/flat_set.hpp b/headers/flat_hpp/flat_set.hpp
index ffec69e..7b0dd73 100644
--- a/headers/flat_hpp/flat_set.hpp
+++ b/headers/flat_hpp/flat_set.hpp
@@ -104,6 +104,14 @@ namespace flat_hpp
             insert(ilist);
         }
 
+        flat_set(flat_set&& other, const Allocator& a)
+        : data_(std::move(other.data_), a)
+        , compare_(std::move(other.compare_)) {}
+
+        flat_set(const flat_set& other, const Allocator& a)
+        : data_(other.data_, a)
+        , compare_(other.compare_) {}
+
         flat_set(flat_set&& other) = default;
         flat_set(const flat_set& other) = default;
 
diff --git a/untests/flat_map_tests.cpp b/untests/flat_map_tests.cpp
index b8b56ef..2d6b976 100644
--- a/untests/flat_map_tests.cpp
+++ b/untests/flat_map_tests.cpp
@@ -177,6 +177,13 @@ TEST_CASE("flat_map") {
             auto s2 = std::move(s1);
             REQUIRE(s1.empty());
             REQUIRE(s2 == map_t{{0,1}, {1,2}});
+            auto s3 = map_t(s2, alloc_t(42));
+            REQUIRE(s2 == s3);
+            REQUIRE(s2.get_allocator().i == 0);
+            REQUIRE(s3.get_allocator().i == 42);
+            auto s4 = map_t(std::move(s3), alloc_t(21));
+            REQUIRE(s3.empty());
+            REQUIRE(s4 == map_t{{0,1}, {1,2}});
         }
 
         {
diff --git a/untests/flat_set_tests.cpp b/untests/flat_set_tests.cpp
index bbc0435..ea6b6af 100644
--- a/untests/flat_set_tests.cpp
+++ b/untests/flat_set_tests.cpp
@@ -161,6 +161,13 @@ TEST_CASE("flat_set") {
             auto s2 = std::move(s1);
             REQUIRE(s1.empty());
             REQUIRE(s2 == set_t{0,1,2});
+            auto s3 = set_t(s2, alloc_t(42));
+            REQUIRE(s2 == s3);
+            REQUIRE(s2.get_allocator().i == 0);
+            REQUIRE(s3.get_allocator().i == 42);
+            auto s4 = set_t(std::move(s3), alloc_t(21));
+            REQUIRE(s3.empty());
+            REQUIRE(s4 == set_t{0,1,2});
         }
 
         {