diff --git a/ext/sqlite3/database.c b/ext/sqlite3/database.c
index 2c949b30..2a7adb09 100644
--- a/ext/sqlite3/database.c
+++ b/ext/sqlite3/database.c
@@ -10,6 +10,10 @@
   if(!_ctxt->db) \
     rb_raise(rb_path2class("SQLite3::Exception"), "cannot use a closed database");
 
+#define REQUIRE_CLOSED_DB(_ctxt) \
+  if(_ctxt->db) \
+    rb_raise(rb_path2class("SQLite3::Exception"), "cannot open a database that is already open");
+
 VALUE cSqlite3Database;
 
 /* See adr/2024-09-fork-safety.md */
@@ -188,6 +192,7 @@ rb_sqlite3_open_v2(VALUE self, VALUE file, VALUE mode, VALUE zvfs)
     int flags;
 
     TypedData_Get_Struct(self, sqlite3Ruby, &database_type, ctx);
+    REQUIRE_CLOSED_DB(ctx);
 
 #if defined TAINTING_SUPPORT
 #  if defined StringValueCStr
@@ -988,6 +993,7 @@ rb_sqlite3_open16(VALUE self, VALUE file)
     sqlite3RubyPtr ctx;
 
     TypedData_Get_Struct(self, sqlite3Ruby, &database_type, ctx);
+    REQUIRE_CLOSED_DB(ctx);
 
 #if defined TAINTING_SUPPORT
 #if defined StringValueCStr
diff --git a/test/test_database.rb b/test/test_database.rb
index 4b02ee6e..95b6f8f9 100644
--- a/test/test_database.rb
+++ b/test/test_database.rb
@@ -66,6 +66,18 @@ def test_segv
       assert_raises { SQLite3::Database.new 1 } # rubocop:disable Minitest/UnspecifiedException
     end
 
+    def test_open_v2_raises_when_database_is_already_open
+      assert_raise(SQLite3::Exception) do
+        db.send(:open_v2, ":memory:", Constants::Open::READWRITE | Constants::Open::CREATE, nil)
+      end
+    end
+
+    def test_open16_raises_when_database_is_already_open
+      assert_raise(SQLite3::Exception) do
+        db.send(:open16, ":memory:".encode(Encoding::UTF_16LE))
+      end
+    end
+
     def test_db_filename
       tf = nil
       assert_equal "", @db.filename("main")