diff --git a/Doxyfile b/Doxyfile
index 37b940a..2790fd2 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -48,7 +48,7 @@ PROJECT_NAME           = fourdst::libcomposition
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = v2.3.0
+PROJECT_NUMBER         = v2.3.1
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewers a
diff --git a/meson.build b/meson.build
index 26eb242..922b2b8 100644
--- a/meson.build
+++ b/meson.build
@@ -18,7 +18,7 @@
 #   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 #
 # *********************************************************************** #
-project('libcomposition', 'cpp', version: 'v2.3.0', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
+project('libcomposition', 'cpp', version: 'v2.3.1', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
 
 # Add default visibility for all C++ targets
 add_project_arguments('-fvisibility=default', language: 'cpp')
diff --git a/src/composition/lib/composition.cpp b/src/composition/lib/composition.cpp
index 1887ff5..ec25c1c 100644
--- a/src/composition/lib/composition.cpp
+++ b/src/composition/lib/composition.cpp
@@ -344,7 +344,7 @@ namespace fourdst::composition {
             throw_unregistered_symbol(getLogger(), std::string(species.name()));
         }
 
-        assert(speciesIndexResult.value() < m_molarAbundances.size());
+        assert(static_cast<size_t>(speciesIndexResult.value()) < m_molarAbundances.size());
 
         m_molarAbundances[speciesIndexResult.value()] = molar_abundance;
         m_cache.clear();