diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b2981a9..2fabe71d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Fix SQL warning when no user session is active during plugin init
 - Fix text area fields alignment
 - Fix error when submitting a form with an hidden question of type `Field`
 - Fixed a bug where a field was deleted when at least one question in a form was linked to another field
diff --git a/inc/questiontype.class.php b/inc/questiontype.class.php
index 1a8e0b6b..6945955d 100644
--- a/inc/questiontype.class.php
+++ b/inc/questiontype.class.php
@@ -381,6 +381,16 @@ private function getAvailableBlocks(): array
         $available_blocks = [];
 
         $entity_restrict = isCommandLine() ? [] : getEntitiesRestrictCriteria(PluginFieldsContainer::getTable(), '', '', true);
+
+        // If entity restriction contains an empty string value, it means no valid session
+        // is active. Running the query would produce a MySQL
+        // warning (1292: Truncated incorrect DECIMAL value)
+        foreach ($entity_restrict as $criterion) {
+            if (is_array($criterion) && in_array('', $criterion, true)) {
+                return $available_blocks;
+            }
+        }
+
         $result           = $field_container->find([
             'is_active' => 1,
             'type'      => 'dom',