diff --git a/changelog/unreleased/decomposedfs-treesize-overflow.md b/changelog/unreleased/decomposedfs-treesize-overflow.md
new file mode 100644
index 0000000000..bff762551f
--- /dev/null
+++ b/changelog/unreleased/decomposedfs-treesize-overflow.md
@@ -0,0 +1,7 @@
+Bugfix: treesize interger overflows
+
+Reading the treesize was parsing the string value as a signed integer while
+setting the treesize used unsigned integers this could cause failures (out of
+range errors) when reading very large treesizes.
+
+https://github.com/cs3org/reva/pull/3963
diff --git a/pkg/storage/utils/decomposedfs/node/node.go b/pkg/storage/utils/decomposedfs/node/node.go
index a2332444a5..ea86aaee29 100644
--- a/pkg/storage/utils/decomposedfs/node/node.go
+++ b/pkg/storage/utils/decomposedfs/node/node.go
@@ -948,11 +948,11 @@ func (n *Node) IsDisabled() bool {
 
 // GetTreeSize reads the treesize from the extended attributes
 func (n *Node) GetTreeSize() (treesize uint64, err error) {
-	s, err := n.XattrInt64(prefixes.TreesizeAttr)
+	s, err := n.XattrUint64(prefixes.TreesizeAttr)
 	if err != nil {
 		return 0, err
 	}
-	return uint64(s), nil
+	return s, nil
 }
 
 // SetTreeSize writes the treesize to the extended attributes
diff --git a/pkg/storage/utils/decomposedfs/node/xattrs.go b/pkg/storage/utils/decomposedfs/node/xattrs.go
index 3aa1eb3d13..d8b526ccd9 100644
--- a/pkg/storage/utils/decomposedfs/node/xattrs.go
+++ b/pkg/storage/utils/decomposedfs/node/xattrs.go
@@ -174,3 +174,12 @@ func (n *Node) XattrInt64(key string) (int64, error) {
 	}
 	return strconv.ParseInt(b, 10, 64)
 }
+
+// XattrUint64 returns the uint64 representation of an attribute
+func (n *Node) XattrUint64(key string) (uint64, error) {
+	b, err := n.XattrString(key)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseUint(b, 10, 64)
+}
diff --git a/pkg/storage/utils/decomposedfs/tree/tree.go b/pkg/storage/utils/decomposedfs/tree/tree.go
index d092f52d65..5ab6d69af5 100644
--- a/pkg/storage/utils/decomposedfs/tree/tree.go
+++ b/pkg/storage/utils/decomposedfs/tree/tree.go
@@ -794,12 +794,17 @@ func (t *Tree) Propagate(ctx context.Context, n *node.Node, sizeDiff int64) (err
 				}
 			case err != nil:
 				return err
+			case sizeDiff > 0:
+				newSize = treeSize + uint64(sizeDiff)
+			case uint64(-sizeDiff) > treeSize:
+				// The sizeDiff is larger than the current treesize. Which would result in
+				// a negative new treesize. Something must have gone wrong with the accounting.
+				// Reset the current treesize to 0.
+				sublog.Error().Uint64("treeSize", treeSize).Int64("sizeDiff", sizeDiff).
+					Msg("Error when updating treesize of parent node. Updated treesize < 0. Reestting to 0")
+				newSize = 0
 			default:
-				if sizeDiff > 0 {
-					newSize = treeSize + uint64(sizeDiff)
-				} else {
-					newSize = treeSize - uint64(-sizeDiff)
-				}
+				newSize = treeSize - uint64(-sizeDiff)
 			}
 
 			// update the tree size of the node