diff --git a/src/core/qgsspatialindex.cpp b/src/core/qgsspatialindex.cpp
index dedbad92a9b8..b03625e03b63 100644
--- a/src/core/qgsspatialindex.cpp
+++ b/src/core/qgsspatialindex.cpp
@@ -67,7 +67,7 @@ QgsSpatialIndex::QgsSpatialIndex()
   RTree::RTreeVariant variant = RTree::RV_RSTAR;
 
   // create R-tree
-  long indexId;
+  SpatialIndex::id_type indexId;
   mRTree = RTree::createNewRTree( *mStorage, fillFactor, indexCapacity,
                                   leafCapacity, dimension, variant, indexId );
 }