diff --git a/eZ/Publish/Core/FieldType/Keyword/KeywordStorage/Gateway/DoctrineStorage.php b/eZ/Publish/Core/FieldType/Keyword/KeywordStorage/Gateway/DoctrineStorage.php
index 5bbe969c625..f7ba605af29 100644
--- a/eZ/Publish/Core/FieldType/Keyword/KeywordStorage/Gateway/DoctrineStorage.php
+++ b/eZ/Publish/Core/FieldType/Keyword/KeywordStorage/Gateway/DoctrineStorage.php
@@ -255,7 +255,7 @@ protected function insertKeywords(array $keywordsToInsert, $contentTypeId)
             foreach (array_keys($keywordsToInsert) as $keyword) {
                 $insertQuery->setParameter(':keyword', $keyword);
                 $insertQuery->execute();
-                $keywordIdMap[$keyword] = $this->connection->lastInsertId(
+                $keywordIdMap[$keyword] = (int)$this->connection->lastInsertId(
                     $this->getSequenceName(self::KEYWORD_TABLE, 'id')
                 );
             }
diff --git a/eZ/Publish/Core/FieldType/Url/UrlStorage/Gateway/DoctrineStorage.php b/eZ/Publish/Core/FieldType/Url/UrlStorage/Gateway/DoctrineStorage.php
index dc42e8d291f..c2b08896d27 100644
--- a/eZ/Publish/Core/FieldType/Url/UrlStorage/Gateway/DoctrineStorage.php
+++ b/eZ/Publish/Core/FieldType/Url/UrlStorage/Gateway/DoctrineStorage.php
@@ -124,7 +124,7 @@ public function insertUrl($url)
 
         $query->execute();
 
-        return $this->connection->lastInsertId(
+        return (int)$this->connection->lastInsertId(
             $this->getSequenceName(self::URL_TABLE, 'id')
         );
     }
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/Gateway/DoctrineDatabase.php b/eZ/Publish/Core/Persistence/Legacy/Content/Gateway/DoctrineDatabase.php
index a585a5b8745..a6f1467abd0 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/Gateway/DoctrineDatabase.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/Gateway/DoctrineDatabase.php
@@ -186,7 +186,7 @@ public function insertContentObject(CreateStruct $struct, $currentVersionNo = 1)
 
         $q->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId(
+        return (int)$this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezcontentobject', 'id')
         );
     }
@@ -275,7 +275,7 @@ public function insertVersion(VersionInfo $versionInfo, array $fields)
 
         $q->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId(
+        return (int)$this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezcontentobject_version', 'id')
         );
     }
@@ -673,7 +673,7 @@ public function insertNewField(Content $content, Field $field, StorageFieldValue
 
         $q->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId(
+        return (int)$this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezcontentobject_attribute', 'id')
         );
     }
@@ -742,7 +742,7 @@ protected function setInsertFieldValues(InsertQuery $q, Content $content, Field
             $q->bindValue($value->sortKeyInt, null, \PDO::PARAM_INT)
         )->set(
             $this->dbHandler->quoteColumn('sort_key_string'),
-            $q->bindValue(mb_substr($value->sortKeyString, 0, 255))
+            $q->bindValue(mb_substr((string)$value->sortKeyString, 0, 255))
         )->set(
             $this->dbHandler->quoteColumn('language_id'),
             $q->bindValue(
@@ -823,7 +823,7 @@ protected function setFieldUpdateValues(UpdateQuery $q, StorageFieldValue $value
             $q->bindValue($value->sortKeyInt, null, \PDO::PARAM_INT)
         )->set(
             $this->dbHandler->quoteColumn('sort_key_string'),
-            $q->bindValue(mb_substr($value->sortKeyString, 0, 255))
+            $q->bindValue(mb_substr((string)$value->sortKeyString, 0, 255))
         );
     }
 
@@ -1310,7 +1310,7 @@ public function listVersionNumbers($contentId)
         $statement = $query->prepare();
         $statement->execute();
 
-        return $statement->fetchAll(\PDO::FETCH_COLUMN);
+        return array_map('intval', $statement->fetchAll(\PDO::FETCH_COLUMN));
     }
 
     /**
@@ -2097,7 +2097,7 @@ public function insertRelation(RelationCreateStruct $createStruct)
 
         $q->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId(
+        return (int)$this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezcontentobject_link', 'id')
         );
     }
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/Location/Gateway/DoctrineDatabase.php b/eZ/Publish/Core/Persistence/Legacy/Content/Location/Gateway/DoctrineDatabase.php
index fe8d94ad6b7..53e19ea3c05 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/Location/Gateway/DoctrineDatabase.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/Location/Gateway/DoctrineDatabase.php
@@ -768,7 +768,7 @@ public function create(CreateStruct $createStruct, array $parentNode)
             );
         $query->prepare()->execute();
 
-        $location->id = $this->handler->lastInsertId($this->handler->getSequenceName('ezcontentobject_tree', 'node_id'));
+        $location->id = (int)$this->handler->lastInsertId($this->handler->getSequenceName('ezcontentobject_tree', 'node_id'));
 
         $mainLocationId = $createStruct->mainLocationId === true ? $location->id : $createStruct->mainLocationId;
         $location->pathString = $parentNode['path_string'] . $location->id . '/';
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/Location/Handler.php b/eZ/Publish/Core/Persistence/Legacy/Content/Location/Handler.php
index 8d7cacbff70..955283cb838 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/Location/Handler.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/Location/Handler.php
@@ -251,8 +251,8 @@ public function copySubtree($sourceId, $destinationParentId, $newOwnerId = null)
             // Copy content
             if (!isset($contentMap[$child['contentobject_id']])) {
                 $content = $this->contentHandler->copy(
-                    $child['contentobject_id'],
-                    $child['contentobject_version'],
+                    (int)$child['contentobject_id'],
+                    (int)$child['contentobject_version'],
                     $newOwnerId
                 );
 
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/Type/Gateway/DoctrineDatabase.php b/eZ/Publish/Core/Persistence/Legacy/Content/Type/Gateway/DoctrineDatabase.php
index 6384900137a..87cd8ee5385 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/Type/Gateway/DoctrineDatabase.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/Type/Gateway/DoctrineDatabase.php
@@ -361,7 +361,8 @@ public function insertType(Type $type, $typeId = null)
 
         $this->insertTypeNameData($typeId, $type->status, $type->name);
 
-        return $typeId;
+        // $typeId passed as the argument could still be non-int
+        return (int)$typeId;
     }
 
     /**
@@ -615,9 +616,9 @@ public function insertFieldDefinition(
 
         $q->prepare()->execute();
 
-        $fieldDefinitionId = $fieldDefinition->id ?? $this->dbHandler->lastInsertId(
+        $fieldDefinitionId = (int)($fieldDefinition->id ?? $this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezcontentclass_attribute', 'id')
-        );
+        ));
 
         foreach ($storageFieldDef->multilingualData as $multilingualData) {
             $this->insertFieldDefinitionMultilingualData($fieldDefinitionId, $multilingualData, $status);
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/UrlAlias/Gateway/DoctrineDatabase.php b/eZ/Publish/Core/Persistence/Legacy/Content/UrlAlias/Gateway/DoctrineDatabase.php
index f9e80f54463..88d8251cb22 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/UrlAlias/Gateway/DoctrineDatabase.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/UrlAlias/Gateway/DoctrineDatabase.php
@@ -709,7 +709,7 @@ public function getNextId()
         }
         $query->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId($sequence);
+        return (int)$this->dbHandler->lastInsertId($sequence);
     }
 
     /**
diff --git a/eZ/Publish/Core/Persistence/Legacy/Content/UrlWildcard/Gateway/DoctrineDatabase.php b/eZ/Publish/Core/Persistence/Legacy/Content/UrlWildcard/Gateway/DoctrineDatabase.php
index 41d4fd859ca..d23d7934898 100644
--- a/eZ/Publish/Core/Persistence/Legacy/Content/UrlWildcard/Gateway/DoctrineDatabase.php
+++ b/eZ/Publish/Core/Persistence/Legacy/Content/UrlWildcard/Gateway/DoctrineDatabase.php
@@ -83,7 +83,7 @@ public function insertUrlWildcard(UrlWildcard $urlWildcard)
 
         $query->prepare()->execute();
 
-        return $this->dbHandler->lastInsertId(
+        return (int)$this->dbHandler->lastInsertId(
             $this->dbHandler->getSequenceName('ezurlwildcard', 'id')
         );
     }