diff --git a/PDAL.spec b/PDAL.spec
index 04bf730..1d50c58 100644
--- a/PDAL.spec
+++ b/PDAL.spec
@@ -9,7 +9,7 @@ Summary:	Point Data Abstraction Library
 Name:		PDAL
 # NOTE: Re-verifiy test exclusions in %%check when updating
 Version:	2.4.3
-Release:	1%{?dist}
+Release:	2%{?dist}
 # The code is licensed BSD except for:
 # - filters/private/csf/* and plugins/i3s/lepcc/* are ASL 2.0
 # - vendor/arbiter/*, plugins/nitf/io/nitflib.h and plugins/oci/io/OciWrapper.* are Expat/MIT
@@ -43,6 +43,10 @@ Patch1:		PDAL_tests.patch
 # fix build with sphinxcontrib-bibtex 2.0 (RHBZ #1921498)
 Patch2:		PDAL_sphinxconf.patch
 
+# Guard against bad return numbers, https://github.com/PDAL/PDAL/pull/3966
+# to be removed with PDAL 2.5.1
+Patch3:         PDAL_bad_return_numbers.patch
+
 BuildRequires:	boost-devel
 BuildRequires:	cmake
 BuildRequires:	eigen3-devel
@@ -246,6 +250,9 @@ sphinx-build -b html . build/html
 %license LICENSE.txt
 
 %changelog
+* Mon Feb 06 2023 Markus Neteler <neteler@mundialis.de> 2.4.3-2
+- patch to guard against bad return numbers (from upstream #3966), to be removed with PDAL 2.5.1
+
 * Sat Aug 06 2022 Sandro Mani <manisandro@gmail.com> - 2.4.3-1
 - Update to 2.4.3
 
diff --git a/PDAL_bad_return_numbers.patch b/PDAL_bad_return_numbers.patch
new file mode 100644
index 0000000..c52ebe9
--- /dev/null
+++ b/PDAL_bad_return_numbers.patch
@@ -0,0 +1,14 @@
+diff --git a/io/private/las/Summary.cpp b/io/private/las/Summary.cpp
+index e9232d4806..91059bfaf9 100644
+--- a/io/private/las/Summary.cpp
++++ b/io/private/las/Summary.cpp
+@@ -57,7 +57,8 @@ void Summary::addPoint(double x, double y, double z, int returnNumber)
+     m_bounds.grow(x, y, z);
+ 
+     // Returns numbers are indexed from one, but the array indexes from 0.
+-    m_returnCounts[returnNumber - 1]++;
++    if (returnNumber >= 1 && returnNumber <= m_returnCounts.size())
++        m_returnCounts[returnNumber - 1]++;
+ }
+ 
+