diff --git a/ext/zlib/zlib.c b/ext/zlib/zlib.c
index 292e640..dc608ee 100644
--- a/ext/zlib/zlib.c
+++ b/ext/zlib/zlib.c
@@ -25,7 +25,7 @@
 # define VALGRIND_MAKE_MEM_UNDEFINED(p, n) 0
 #endif
 
-#define RUBY_ZLIB_VERSION "3.0.0"
+#define RUBY_ZLIB_VERSION "3.1.0"
 
 #ifndef RB_PASS_CALLED_KEYWORDS
 # define rb_class_new_instance_kw(argc, argv, klass, kw_splat) rb_class_new_instance(argc, argv, klass)