diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp
index 763fd95783..8ec9720ee7 100644
--- a/include/nlohmann/json.hpp
+++ b/include/nlohmann/json.hpp
@@ -3401,6 +3401,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         }
 
         m_data.m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
+        set_parents();
     }
 
     /// @brief updates a JSON object from another object, overwriting existing keys
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 7979227a05..0164992148 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -22948,6 +22948,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         }
 
         m_data.m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
+        set_parents();
     }
 
     /// @brief updates a JSON object from another object, overwriting existing keys
diff --git a/tests/src/unit-diagnostics.cpp b/tests/src/unit-diagnostics.cpp
index 345d6eee29..472d11e283 100644
--- a/tests/src/unit-diagnostics.cpp
+++ b/tests/src/unit-diagnostics.cpp
@@ -242,4 +242,24 @@ TEST_CASE("Regression tests for extended diagnostics")
             json const j_arr_copy = j_arr;
         }
     }
+
+    SECTION("Regression test for issue #3915 - JSON_DIAGNOSTICS trigger assertion")
+    {
+        json j = json::object();
+        j["root"] = "root_str";
+
+        json jj = json::object();
+        jj["child"] = json::object();
+
+        // If do not push anything in object, then no assert will be produced
+        jj["child"]["prop1"] = "prop1_value";
+
+        // Push all properties of child in parent
+        j.insert(jj.at("child").begin(), jj.at("child").end());
+
+        // Here assert is generated when construct new json
+        const json k(j);
+
+        CHECK(k.dump() == "{\"prop1\":\"prop1_value\",\"root\":\"root_str\"}");
+    }
 }