diff --git a/lib/Tools/Db/ExtendedQueryBuilder.php b/lib/Tools/Db/ExtendedQueryBuilder.php
index 3911bd08..e7c955fb 100644
--- a/lib/Tools/Db/ExtendedQueryBuilder.php
+++ b/lib/Tools/Db/ExtendedQueryBuilder.php
@@ -44,6 +44,7 @@
 use OCA\FilesLock\Tools\Traits\TArrayTools;
 use OCP\DB\QueryBuilder\ICompositeExpression;
 use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\DB\QueryBuilder\IQueryFunction;
 use OCP\IDBConnection;
 use OCP\ILogger;
 use Psr\Log\LoggerInterface;
@@ -271,7 +272,7 @@ public function exprFieldWithinJsonFormat(
 			$func->concat($fieldRight, $qb->createNamedParameter('"%'))
 		);
 
-		return $expr->iLike($alias . '.' . $field, $concat);
+		return (string)$expr->iLike($alias . '.' . $field, $concat);
 	}
 
 
@@ -303,7 +304,7 @@ public function exprValueWithinJsonFormat(
 			$comp = 'notLike';
 		}
 
-		return $expr->$comp($field, $qb->createNamedParameter('%"' . $value . '"%'));
+		return (string)$expr->$comp($field, $qb->createNamedParameter('%"' . $value . '"%'));
 	}
 
 
@@ -428,9 +429,9 @@ public function exprLike(string $field, string $value, string $alias = '', bool
 
 		$expr = $this->expr();
 		if ($cs) {
-			return $expr->like($field, $this->createNamedParameter($value));
+			return (string)$expr->like($field, $this->createNamedParameter($value));
 		} else {
-			return $expr->iLike($field, $this->createNamedParameter($value));
+			return (string)$expr->iLike($field, $this->createNamedParameter($value));
 		}
 	}
 
@@ -450,11 +451,11 @@ public function exprLimit(string $field, string $value, string $alias = '', bool
 
 		$expr = $this->expr();
 		if ($cs) {
-			return $expr->eq($field, $this->createNamedParameter($value));
+			return (string)$expr->eq($field, $this->createNamedParameter($value));
 		} else {
 			$func = $this->func();
 
-			return $expr->eq($func->lower($field), $func->lower($this->createNamedParameter($value)));
+			return (string)$expr->eq($func->lower($field), $func->lower($this->createNamedParameter($value)));
 		}
 	}
 
@@ -473,7 +474,7 @@ public function exprLimitInt(string $field, int $value, string $alias = ''): str
 
 		$expr = $this->expr();
 
-		return $expr->eq($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
+		return (string)$expr->eq($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
 	}
 
 
@@ -592,7 +593,7 @@ public function exprLimitInArray(string $field, array $values, string $alias = '
 
 		$expr = $this->expr();
 
-		return $expr->in($field, $this->createNamedParameter($values, IQueryBuilder::PARAM_STR_ARRAY));
+		return (string)$expr->in($field, $this->createNamedParameter($values, IQueryBuilder::PARAM_STR_ARRAY));
 	}
 
 
@@ -610,7 +611,7 @@ public function exprLimitBitwise(string $field, int $flag, string $alias = ''):
 
 		$expr = $this->expr();
 
-		return $expr->gt(
+		return (string)$expr->gt(
 			$expr->bitwiseAnd($field, $flag),
 			$this->createNamedParameter(0, IQueryBuilder::PARAM_INT)
 		);
@@ -633,9 +634,9 @@ public function exprLt(string $field, int $value, bool $lte = false, string $ali
 		$expr = $this->expr();
 
 		if ($lte) {
-			return $expr->lte($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
+			return (string)$expr->lte($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
 		} else {
-			return $expr->lt($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
+			return (string)$expr->lt($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
 		}
 	}
 
@@ -655,9 +656,9 @@ public function exprGt(string $field, int $value, bool $gte = false, string $ali
 		$expr = $this->expr();
 
 		if ($gte) {
-			return $expr->gte($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
+			return (string)$expr->gte($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
 		} else {
-			return $expr->gt($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
+			return (string)$expr->gt($field, $this->createNamedParameter($value, IQueryBuilder::PARAM_INT));
 		}
 	}
 
@@ -763,11 +764,11 @@ public function exprUnlike(string $field, string $value, string $alias = '', boo
 
 		$expr = $this->expr();
 		if ($cs) {
-			return $expr->notLike($field, $this->createNamedParameter($value));
+			return (string)$expr->notLike($field, $this->createNamedParameter($value));
 		} else {
 			$func = $this->func();
 
-			return $expr->notLike($func->lower($field), $func->lower($this->createNamedParameter($value)));
+			return (string)$expr->notLike($func->lower($field), $func->lower($this->createNamedParameter($value)));
 		}
 	}