diff --git a/src/core/qgsauxiliarystorage.cpp b/src/core/qgsauxiliarystorage.cpp
index 61e2f62bbd6..712c29d8b74 100644
--- a/src/core/qgsauxiliarystorage.cpp
+++ b/src/core/qgsauxiliarystorage.cpp
@@ -626,15 +626,33 @@ bool QgsAuxiliaryStorage::duplicateTable( const QgsDataSourceUri &ogrUri, const
   return rc;
 }
 
-bool QgsAuxiliaryStorage::saveAs( const QString &filename ) const
+QString QgsAuxiliaryStorage::errorString() const
 {
-  if ( QFile::exists( filename ) )
-    QFile::remove( filename );
-
-  return  QFile::copy( currentFileName(), filename );
+  return mErrorString;
 }
 
-bool QgsAuxiliaryStorage::saveAs( const QgsProject &project ) const
+bool QgsAuxiliaryStorage::saveAs( const QString &filename )
+{
+  mErrorString.clear();
+
+  QFile dest( filename );
+  if ( dest.exists() && !dest.remove() )
+  {
+    mErrorString = dest.errorString();
+    return false;
+  }
+
+  QFile origin( currentFileName() );
+  if ( !origin.copy( filename ) )
+  {
+    mErrorString = origin.errorString();
+    return false;
+  }
+
+  return true;
+}
+
+bool QgsAuxiliaryStorage::saveAs( const QgsProject &project )
 {
   return saveAs( filenameForProject( project ) );
 }
diff --git a/src/core/qgsauxiliarystorage.h b/src/core/qgsauxiliarystorage.h
index 181c842f371..04d56ee3f7c 100644
--- a/src/core/qgsauxiliarystorage.h
+++ b/src/core/qgsauxiliarystorage.h
@@ -319,12 +319,14 @@ class CORE_EXPORT QgsAuxiliaryStorage
      */
     QString currentFileName() const;
 
+    QString errorString() const;
+
     /**
      * Saves the current database to a new path.
      *
      * \returns true if everything is saved, false otherwise
      */
-    bool saveAs( const QString &filename ) const;
+    bool saveAs( const QString &filename );
 
     /**
      * Saves the current database to a new path for a specific project.
@@ -333,7 +335,7 @@ class CORE_EXPORT QgsAuxiliaryStorage
      *
      * \returns true if everything is saved, false otherwise
      */
-    bool saveAs( const QgsProject &project ) const;
+    bool saveAs( const QgsProject &project );
 
     /**
      * Saves the current database.
@@ -408,6 +410,7 @@ class CORE_EXPORT QgsAuxiliaryStorage
     QString mFileName; // original filename
     QString mTmpFileName; // temporary filename used in copy mode
     bool mCopy = false;
+    QString mErrorString;
 };
 
 #endif
diff --git a/src/core/qgsproject.cpp b/src/core/qgsproject.cpp
index a166d41f86c..93108f82ad6 100644
--- a/src/core/qgsproject.cpp
+++ b/src/core/qgsproject.cpp
@@ -1649,7 +1649,10 @@ bool QgsProject::write()
 
     // errors raised during writing project file are more important
     if ( !asOk && writeOk )
-      setError( tr( "Unable to save auxiliary storage" ) );
+    {
+      const QString err = mAuxiliaryStorage->errorString();
+      setError( tr( "Unable to save auxiliary storage ('%1')" ).arg( err ) );
+    }
 
     return asOk && writeOk;
   }
@@ -2614,7 +2617,8 @@ bool QgsProject::zip( const QString &filename )
 
   if ( ! saveAuxiliaryStorage( asFileName ) )
   {
-    setError( tr( "Unable to save auxiliary storage" ) );
+    const QString err = mAuxiliaryStorage->errorString();
+    setError( tr( "Unable to save auxiliary storage ('%1')" ).arg( err ) );
     return false;
   }