diff --git a/lib/private/Files/Cache/Propagator.php b/lib/private/Files/Cache/Propagator.php
index 989a4d0c7d..41b4c2bb07 100644
--- a/lib/private/Files/Cache/Propagator.php
+++ b/lib/private/Files/Cache/Propagator.php
@@ -91,7 +91,7 @@ class Propagator implements IPropagator {
 		}, $parentHashes);
 
 		$builder->update('filecache')
-			->set('mtime', $builder->createFunction('GREATEST(' . $builder->getColumnName('mtime') . ', ' . $builder->createNamedParameter((int)$time, IQueryBuilder::PARAM_INT) . ')'))
+			->set('mtime', $builder->func()->greatest('mtime', $builder->createNamedParameter((int)$time, IQueryBuilder::PARAM_INT)))
 			->set('etag', $builder->createNamedParameter($etag, IQueryBuilder::PARAM_STR))
 			->where($builder->expr()->eq('storage', $builder->createNamedParameter($storageId, IQueryBuilder::PARAM_INT)))
 			->andWhere($builder->expr()->in('path_hash', $hashParams));
@@ -102,7 +102,10 @@ class Propagator implements IPropagator {
 			// we need to do size separably so we can ignore entries with uncalculated size
 			$builder = $this->connection->getQueryBuilder();
 			$builder->update('filecache')
-				->set('size', $builder->func()->add('size', $builder->createNamedParameter($sizeDifference)))
+				->set('size', $builder->func()->greatest(
+					$builder->createNamedParameter(-1, IQueryBuilder::PARAM_INT),
+					$builder->func()->add('size', $builder->createNamedParameter($sizeDifference)))
+				)
 				->where($builder->expr()->eq('storage', $builder->createNamedParameter($storageId, IQueryBuilder::PARAM_INT)))
 				->andWhere($builder->expr()->in('path_hash', $hashParams))
 				->andWhere($builder->expr()->gt('size', $builder->expr()->literal(-1, IQueryBuilder::PARAM_INT)));
diff --git a/tests/lib/Files/Cache/PropagatorTest.php b/tests/lib/Files/Cache/PropagatorTest.php
index 402b29c8c3..bcd808a840 100644
--- a/tests/lib/Files/Cache/PropagatorTest.php
+++ b/tests/lib/Files/Cache/PropagatorTest.php
@@ -81,6 +81,17 @@ class PropagatorTest extends TestCase {
 		}
 	}
 
+	public function testSizePropagationNoNegative() {
+		$paths = ['', 'foo', 'foo/bar'];
+		$oldInfos = $this->getFileInfos($paths);
+		$this->storage->getPropagator()->propagateChange('foo/bar/file.txt', time(), -100);
+		$newInfos = $this->getFileInfos($paths);
+
+		foreach ($oldInfos as $i => $oldInfo) {
+			$this->assertEquals(-1, $newInfos[$i]->getSize());
+		}
+	}
+
 	public function testBatchedPropagation() {
 		$this->storage->mkdir('foo/baz');
 		$this->storage->mkdir('asd');