--- libgeos/geos/include/geos/index/strtree/TemplateSTRtree.h.orig	2021-11-18 21:07:45.622785813 +0100
+++ libgeos/geos/include/geos/index/strtree/TemplateSTRtree.h	2021-11-18 21:09:00.690195225 +0100
@@ -359,12 +359,12 @@
 
         // begin and end define a range of nodes needing parents
         auto begin = nodes.begin();
-        auto end = nodes.end();
+        auto number = static_cast<size_t>(std::distance(begin, nodes.end()));
 
-        while (std::distance(begin, end) > 1) {
-            createParentNodes(begin, end);
-            begin = end; // parents just added become children in the next round
-            end = nodes.end();
+        while (number > 1) {
+            createParentNodes(begin, number);
+            std::advance(begin, static_cast<long>(number)); // parents just added become children in the next round
+            number = static_cast<size_t>(std::distance(begin, nodes.end()));
         }
 
         assert(finalSize == nodes.size());
@@ -421,22 +421,24 @@
         return nodesInTree;
     }
 
-    void createParentNodes(const NodeListIterator& begin, const NodeListIterator& end) {
+    void createParentNodes(const NodeListIterator& begin, size_t number) {
         // Arrange child nodes in two dimensions.
         // First, divide them into vertical slices of a given size (left-to-right)
         // Then create nodes within those slices (bottom-to-top)
-        auto numChildren = static_cast<std::size_t>(std::distance(begin, end));
-        auto numSlices = sliceCount(numChildren);
-        std::size_t nodesPerSlice = sliceCapacity(numChildren, numSlices);
+        auto numSlices = sliceCount(number);
+        std::size_t nodesPerSlice = sliceCapacity(number, numSlices);
 
         // We could sort all of the nodes here, but we don't actually need them to be
         // completely sorted. They need to be sorted enough for each node to end up
         // in the right vertical slice, but their relative position within the slice
         // doesn't matter. So we do a partial sort for each slice below instead.
+        auto end = begin + static_cast<long>(number);
         sortNodesX(begin, end);
 
         auto startOfSlice = begin;
         for (decltype(numSlices) j = 0; j < numSlices; j++) {
+            // end iterator is being invalidated at each iteration
+            end = begin + static_cast<long>(number);
             auto nodesRemaining = static_cast<size_t>(std::distance(startOfSlice, end));
             auto nodesInSlice = std::min(nodesRemaining, nodesPerSlice);
             auto endOfSlice = std::next(startOfSlice, static_cast<long>(nodesInSlice));