diff --git a/lib/server/commands/Propfind.js b/lib/server/commands/Propfind.js
index 237301f4..6d51e956 100644
--- a/lib/server/commands/Propfind.js
+++ b/lib/server/commands/Propfind.js
@@ -196,7 +196,7 @@ function default_1(arg, callback) {
                             }); });
                             resource.size(targetSource, function (e, size) { return process.nextTick(function () {
                                 if (!e)
-                                    prop.ele('D:getcontentlength').add(size);
+                                    prop.ele('D:getcontentlength').add(size === undefined || size === null || size.constructor !== Number ? 0 : size);
                                 nbOut(e);
                             }); });
                         }
diff --git a/src/server/commands/Propfind.ts b/src/server/commands/Propfind.ts
index eee6b7b1..69d1cc32 100644
--- a/src/server/commands/Propfind.ts
+++ b/src/server/commands/Propfind.ts
@@ -254,7 +254,7 @@ export default function(arg : MethodCallArgs, callback)
                             }))
                             resource.size(targetSource, (e, size) => process.nextTick(() => {
                                 if(!e)
-                                    prop.ele('D:getcontentlength').add(size)
+                                    prop.ele('D:getcontentlength').add(size === undefined || size === null || size.constructor !== Number ? 0 : size)
                                 nbOut(e);
                             }))
                         }