diff --git a/arangod/MMFiles/MMFilesSkiplistIndex.cpp b/arangod/MMFiles/MMFilesSkiplistIndex.cpp
index 123a7f4b4d..6c635ec348 100644
--- a/arangod/MMFiles/MMFilesSkiplistIndex.cpp
+++ b/arangod/MMFiles/MMFilesSkiplistIndex.cpp
@@ -1430,9 +1430,9 @@ arangodb::aql::AstNode* MMFilesSkiplistIndex::specializeCondition(
     }
 
     std::sort(nodes.begin(), nodes.end(),
-              [](arangodb::aql::AstNode const* lhs,
+              [this](arangodb::aql::AstNode const* lhs,
                  arangodb::aql::AstNode const* rhs) -> bool {
-                return Index::sortWeight(lhs) < Index::sortWeight(rhs);
+                return this->sortWeight(lhs) < this->sortWeight(rhs);
               });
 
     lastContainsEquality = containsEquality;