diff --git a/CHANGELOG b/CHANGELOG
index bea6875..aea0472 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -3,6 +3,7 @@ v0.7.1 (unreleased):
 - Modernize packaging.
 - Explicitly support $WITH_EXTENSION/$WITHOUT_EXTENSION to control whether the
   C tokenizer should be built.
+- Fix building in C23 (e.g. in GCC 15). (#340)
 
 v0.7.0 (released June 28, 2025):
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 22f4bca..007f890 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -10,6 +10,8 @@ Unreleased
 - Modernize packaging.
 - Explicitly support ``$WITH_EXTENSION`` / ``$WITHOUT_EXTENSION`` to control
   whether the C tokenizer should be built.
+- Fix building in C23 (e.g. in GCC 15).
+  (`#340 <https://github.com/earwig/mwparserfromhell/issues/340>`_)
 
 v0.7.0
 ------
diff --git a/src/mwparserfromhell/parser/ctokenizer/avl_tree.c b/src/mwparserfromhell/parser/ctokenizer/avl_tree.c
index 8516691..9a093cd 100644
--- a/src/mwparserfromhell/parser/ctokenizer/avl_tree.c
+++ b/src/mwparserfromhell/parser/ctokenizer/avl_tree.c
@@ -21,7 +21,9 @@
 #define false 0
 #define true  1
 
+#if __STDC_VERSION__ < 202000
 typedef int bool;
+#endif
 
 #include "avl_tree.h"