diff --git a/ScadaAdmin/OpenExtensions/ExtImport/Forms/FrmImportFile.cs b/ScadaAdmin/OpenExtensions/ExtImport/Forms/FrmImportFile.cs
index dfca00d9f..139f00404 100644
--- a/ScadaAdmin/OpenExtensions/ExtImport/Forms/FrmImportFile.cs
+++ b/ScadaAdmin/OpenExtensions/ExtImport/Forms/FrmImportFile.cs
@@ -617,18 +617,24 @@ private void button3_Click(object sender, EventArgs e)
         /// <param name="e"></param>
         private void button1_Click(object sender, EventArgs e)
         {
-
-            //Then, we generate a device configuration according to imported rows
-            bool doNext = ImportDeviceConfiguration();
-
-            if (doNext)
+            if (string.IsNullOrEmpty(textBox4.Text))
             {
-                //save the default byte order in project config
-                string extImportConfigPath = string.Format("{0}\\Instances\\Default\\ExtImport\\extImportConfig.xml", project.ProjectDir);
-                SaveExtImportConfig(extImportConfigPath);
+                MessageBox.Show("Please fill the adress gap input", "Attention", MessageBoxButtons.OK, MessageBoxIcon.Error);
+            }
+            else
+            {
+                //Then, we generate a device configuration according to imported rows
+                bool doNext = ImportDeviceConfiguration();
+
+                if (doNext)
+                {
+                    //save the default byte order in project config
+                    string extImportConfigPath = string.Format("{0}\\Instances\\Default\\ExtImport\\extImportConfig.xml", project.ProjectDir);
+                    SaveExtImportConfig(extImportConfigPath);
 
-                //Finally, we close the form
-                DialogResult = DialogResult.OK;
+                    //Finally, we close the form
+                    DialogResult = DialogResult.OK;
+                }
             }
         }