diff --git a/app-common/src/main/java/im/angry/openeuicc/ui/wizard/DownloadWizardDetailsFragment.kt b/app-common/src/main/java/im/angry/openeuicc/ui/wizard/DownloadWizardDetailsFragment.kt
index 4f66307..007e4c0 100644
--- a/app-common/src/main/java/im/angry/openeuicc/ui/wizard/DownloadWizardDetailsFragment.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/ui/wizard/DownloadWizardDetailsFragment.kt
@@ -79,13 +79,19 @@ class DownloadWizardDetailsFragment : DownloadWizardActivity.DownloadWizardStepF
 
     private fun validate() {
         smdp.error = smdp.editText!!.text?.let {
-            if (Patterns.DOMAIN_NAME.matcher(smdp.editText!!.text).matches()) return@let null
-            getString(R.string.download_wizard_error_invalid_address_format)
+            when {
+                it.isEmpty() -> getString(R.string.download_wizard_error_address_required)
+                it.contains("://") -> getString(R.string.download_wizard_error_cannot_url)
+                Patterns.DOMAIN_NAME.matcher(it).matches() -> null
+                else -> getString(R.string.download_wizard_error_address_invalid_format)
+            }
         }
         imei.error = imei.editText!!.text?.let {
-            if (it.isEmpty()) return@let null
-            if (it.length == 15 && luhnValid(it)) return@let null
-            getString(R.string.download_wizard_error_invalid_imei_format)
+            when {
+                it.isEmpty() -> null
+                it.length == 15 && luhnValid(it) -> null
+                else -> getString(R.string.download_wizard_error_imei_invalid_format)
+            }
         }
     }
 }
diff --git a/app-common/src/main/res/values/strings.xml b/app-common/src/main/res/values/strings.xml
index 94f7f7a..13d765f 100644
--- a/app-common/src/main/res/values/strings.xml
+++ b/app-common/src/main/res/values/strings.xml
@@ -98,8 +98,10 @@
     <string name="download_wizard_diagnostics_last_apdu_exception">Last APDU exception:</string>
     <string name="download_wizard_diagnostics_save">Save</string>
     <string name="download_wizard_diagnostics_file_template">Diagnostics at %s</string>
-    <string name="download_wizard_error_invalid_address_format">Invalid SM-DP+ address</string>
-    <string name="download_wizard_error_invalid_imei_format">Invalid IMEI format</string>
+    <string name="download_wizard_error_address_required">Server address is required</string>
+    <string name="download_wizard_error_cannot_url">Server address not is URL</string>
+    <string name="download_wizard_error_address_invalid_format">Invalid Server address</string>
+    <string name="download_wizard_error_imei_invalid_format">Invalid IMEI format</string>
 
     <string name="logs_saved_message">Logs have been saved to the selected path. Would you like to share the log through another app?</string>