--- libproj/proj/src/iso19111/io.cpp.orig	2021-11-18 21:04:10.708477463 +0100
+++ libproj/proj/src/iso19111/io.cpp	2021-11-18 21:04:13.528455257 +0100
@@ -7675,7 +7675,7 @@
                 iterCur = steps.erase(iterPrev, std::next(iterCur));
                 if (iterCur != steps.begin())
                     iterCur = std::prev(iterCur);
-                if (iterCur == steps.begin())
+                if (iterCur == steps.begin() && iterCur != steps.end())
                     ++iterCur;
             };