diff --git a/CHANGELOG.md b/CHANGELOG.md
index a69fde81..95e0b396 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog for RCMCardDAV
 
+## Version 4.4.5 (to 4.4.4)
+
+- Fix: Internal server error with PHP8 when searching address fields of contacts (Fixes: #410)
+
 ## Version 4.4.4 (to 4.4.3)
 
 - Fix PHP 8.1 warning on loss of precision by using integer division
diff --git a/src/Addressbook.php b/src/Addressbook.php
index f45212ed..160e499d 100644
--- a/src/Addressbook.php
+++ b/src/Addressbook.php
@@ -40,6 +40,7 @@
 /**
  * @psalm-import-type FullAbookRow from AbstractDatabase
  * @psalm-import-type SaveData from DataConversion
+ * @psalm-import-type SaveDataAddressField from DataConversion
  *
  * @psalm-type GroupSaveData = array{
  *   ID: string,
@@ -1763,6 +1764,16 @@ private function checkPostSearchFilter(
             }
         }
 
+        // normalize address structured data to string
+        if (isset($save_data['address'])) {
+            $mergedAddrs = [];
+            /** @psalm-var list<SaveDataAddressField> $save_data['address'] */
+            foreach ($save_data['address'] as $addrStruct) {
+                $mergedAddrs[] = implode(' ', $addrStruct);
+            }
+            $save_data['address'] = $mergedAddrs;
+        }
+
         $filterMatches = 0;
         foreach ($postSearchFilter as $psfilter) {
             [ $col, $val ] = $psfilter;
diff --git a/src/DataConversion.php b/src/DataConversion.php
index df03859c..ba9213c4 100644
--- a/src/DataConversion.php
+++ b/src/DataConversion.php
@@ -58,7 +58,7 @@
  *     maidenname?: string,
  *     organization?: string,
  *     department?: string
- * } & array<string, SaveDataMultiField|SaveDataAddressField>
+ * } & array<string, SaveDataMultiField|list<SaveDataAddressField>>
  *
  * @psalm-type SaveDataFromDC = array{
  *     name: string,
@@ -83,7 +83,7 @@
  *     department?: string,
  *     vcard?: string,
  *     _carddav_vcard?: VCard,
- * } & array<string, SaveDataMultiField|SaveDataAddressField>
+ * } & array<string, SaveDataMultiField|list<SaveDataAddressField>>
  *
  * @psalm-type ColTypeDef = array{subtypes?: list<string>, subtypealias?: array<string,string>}
  * @psalm-type ColTypeDefs = array<string,ColTypeDef>
diff --git a/tests/unit/AddressbookTest.php b/tests/unit/AddressbookTest.php
index c295277a..1c348ca1 100644
--- a/tests/unit/AddressbookTest.php
+++ b/tests/unit/AddressbookTest.php
@@ -314,6 +314,13 @@ public function searchDataProvider(): array
                 [], [],
                 2, ["60", "50"]
             ],
+            'Single Multivalue DB structured-content field search with contains search' => [
+                ['address'], ["Kanto"], rcube_addressbook::SEARCH_ALL, true, false,
+                'name', 'ASC', 1, 10,
+                0,
+                [], [],
+                1, ["60"]
+            ],
             'Single Multivalue DB field search with strict search' => [
                 ['email'], ["north@7kingdoms.com"], rcube_addressbook::SEARCH_STRICT, true, false,
                 'name', 'ASC', 1, 10,
@@ -372,6 +379,14 @@ public function searchDataProvider(): array
                 [], [],
                 1, ["60"]
             ],
+            'All fields search (no matches)' => [
+                '*', 'Birkin22',
+                rcube_addressbook::SEARCH_ALL, true, false,
+                'name', 'ASC', 1, 10,
+                0,
+                [], [],
+                0, []
+            ],
             'Two fields OR search' => [
                 ['organization', 'name'], 'the',
                 rcube_addressbook::SEARCH_ALL, true, false,