diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
index 6856a0965..fa5eb62b0 100644
--- a/include/nlohmann/detail/conversions/from_json.hpp
+++ b/include/nlohmann/detail/conversions/from_json.hpp
@@ -398,6 +398,34 @@ inline void from_json(const BasicJsonType& j, CompatibleArrayType& bin)
     }
 }
 
+template<typename BasicJsonType, typename ConstructibleObjectType>
+auto from_json_object_impl(const BasicJsonType& j, ConstructibleObjectType& obj, priority_tag<1> /*unused*/)
+-> decltype(
+    obj.reserve(std::declval<typename ConstructibleObjectType::size_type>()),
+    void())
+{
+    ConstructibleObjectType ret;
+    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
+    ret.reserve(inner_object->size());
+    for (const auto& p : *inner_object)
+    {
+        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
+    }
+    obj = std::move(ret);
+}
+
+template<typename BasicJsonType, typename ConstructibleObjectType>
+inline void from_json_object_impl(const BasicJsonType& j, ConstructibleObjectType& obj, priority_tag<0> /*unused*/)
+{
+    ConstructibleObjectType ret;
+    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
+    for (const auto& p : *inner_object)
+    {
+        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
+    }
+    obj = std::move(ret);
+}
+
 template<typename BasicJsonType, typename ConstructibleObjectType,
          enable_if_t<is_constructible_object_type<BasicJsonType, ConstructibleObjectType>::value, int> = 0>
 inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
@@ -407,13 +435,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
         JSON_THROW(type_error::create(302, concat("type must be object, but is ", j.type_name()), &j));
     }
 
-    ConstructibleObjectType ret;
-    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
-    for (const auto& p : *inner_object)
-    {
-        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
-    }
-    obj = std::move(ret);
+    from_json_object_impl(j, obj, priority_tag<1> {});
 }
 
 // overload for arithmetic types, not chosen for basic_json template arguments
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 31bfb869d..4e484d764 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -5693,6 +5693,34 @@ inline void from_json(const BasicJsonType& j, CompatibleArrayType& bin)
     }
 }
 
+template<typename BasicJsonType, typename ConstructibleObjectType>
+auto from_json_object_impl(const BasicJsonType& j, ConstructibleObjectType& obj, priority_tag<1> /*unused*/)
+-> decltype(
+    obj.reserve(std::declval<typename ConstructibleObjectType::size_type>()),
+    void())
+{
+    ConstructibleObjectType ret;
+    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
+    ret.reserve(inner_object->size());
+    for (const auto& p : *inner_object)
+    {
+        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
+    }
+    obj = std::move(ret);
+}
+
+template<typename BasicJsonType, typename ConstructibleObjectType>
+inline void from_json_object_impl(const BasicJsonType& j, ConstructibleObjectType& obj, priority_tag<0> /*unused*/)
+{
+    ConstructibleObjectType ret;
+    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
+    for (const auto& p : *inner_object)
+    {
+        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
+    }
+    obj = std::move(ret);
+}
+
 template<typename BasicJsonType, typename ConstructibleObjectType,
          enable_if_t<is_constructible_object_type<BasicJsonType, ConstructibleObjectType>::value, int> = 0>
 inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
@@ -5702,13 +5730,7 @@ inline void from_json(const BasicJsonType& j, ConstructibleObjectType& obj)
         JSON_THROW(type_error::create(302, concat("type must be object, but is ", j.type_name()), &j));
     }
 
-    ConstructibleObjectType ret;
-    const auto* inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
-    for (const auto& p : *inner_object)
-    {
-        ret.emplace(p.first, p.second.template get<typename ConstructibleObjectType::mapped_type>());
-    }
-    obj = std::move(ret);
+    from_json_object_impl(j, obj, priority_tag<1> {});
 }
 
 // overload for arithmetic types, not chosen for basic_json template arguments
diff --git a/tests/src/unit-conversions.cpp b/tests/src/unit-conversions.cpp
index 1937affbb..4975854c0 100644
--- a/tests/src/unit-conversions.cpp
+++ b/tests/src/unit-conversions.cpp
@@ -1389,6 +1389,37 @@ TEST_CASE("value conversion")
                 // CHECK(m5["one"] == "eins");
             }
 
+            SECTION("reserve is called on containers that support it (#5406)")
+            {
+                // build a larger object so that a missing/incorrect reserve()
+                // call would be more likely to corrupt or drop elements
+                json j_large;
+                for (int i = 0; i < 100; ++i)
+                {
+                    j_large[std::to_string(i)] = i;
+                }
+
+                SECTION("std::unordered_map (supports reserve)")
+                {
+                    const auto m = j_large.get<std::unordered_map<std::string, int>>();
+                    CHECK(m.size() == 100);
+                    for (int i = 0; i < 100; ++i)
+                    {
+                        CHECK(m.at(std::to_string(i)) == i);
+                    }
+                }
+
+                SECTION("std::map (no reserve, fallback path)")
+                {
+                    const auto m = j_large.get<std::map<std::string, int>>();
+                    CHECK(m.size() == 100);
+                    for (int i = 0; i < 100; ++i)
+                    {
+                        CHECK(m.at(std::to_string(i)) == i);
+                    }
+                }
+            }
+
             SECTION("std::multimap")
             {
                 j1.get<std::multimap<std::string, int>>();