diff --git a/uSync.Core/Mapping/SyncValueMapperCollection.cs b/uSync.Core/Mapping/SyncValueMapperCollection.cs
index 4d15b51f..df3c0b33 100644
--- a/uSync.Core/Mapping/SyncValueMapperCollection.cs
+++ b/uSync.Core/Mapping/SyncValueMapperCollection.cs
@@ -55,7 +55,7 @@ public string GetExportValue(object value, string editorAlias)
                     mappedValue = mapper.GetExportValue(mappedValue, editorAlias);
                 }
 
-                return mappedValue;
+                return mappedValue ?? string.Empty;
             }
 
             return GetSafeValue(value);