diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7b4f27e..275ea1d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 2.6...3.0.2)
 
-project(xbyak LANGUAGES CXX VERSION 6.06)
+project(xbyak LANGUAGES CXX VERSION 6.60)
 
 file(GLOB headers xbyak/*.h)
 
diff --git a/doc/changelog.md b/doc/changelog.md
index 3a921e9..ddb91e4 100644
--- a/doc/changelog.md
+++ b/doc/changelog.md
@@ -1,5 +1,6 @@
 # History
 
+* 2022/Jun/06 ver 6.60 change the version format to avoid it going backward
 * 2022/Jun/01 ver 6.06 refactor Cpu::Type class and improve MmapAllocator when XBYAK_USE_MEMFD is defined.
 * 2022/Mar/20 ver 6.052 add Cpu::operator==()
 * 2022/Mar/13 ver 6.051 fix compile error when XBYAK_NO_EXCEPTION is defined
diff --git a/gen/gen_code.cpp b/gen/gen_code.cpp
index 4cfcc1e..a8b169e 100644
--- a/gen/gen_code.cpp
+++ b/gen/gen_code.cpp
@@ -252,7 +252,7 @@
 		char buf[16];
 		unsigned int v = VERSION;
 		if (v & 0xF) {
-			snprintf(buf, sizeof(buf), "%d.%02X%x", v >> 12, (v >> 4) & 0xFF, v & 0xF);
+			snprintf(buf, sizeof(buf), "%d.%02X.%x", v >> 12, (v >> 4) & 0xFF, v & 0xF);
 		} else {
 			snprintf(buf, sizeof(buf), "%d.%02X", v >> 12, (v >> 4) & 0xFF);
 		}
diff --git a/meson.build b/meson.build
index 38d2430..63d9310 100644
--- a/meson.build
+++ b/meson.build
@@ -5,7 +5,7 @@
 project(
 	'xbyak',
 	'cpp',
-	version: '6.06',
+	version: '6.60',
 	license: 'BSD-3-Clause',
 	default_options: 'b_ndebug=if-release'
 )
diff --git a/readme.md b/readme.md
index 68bd890..ede8f26 100644
--- a/readme.md
+++ b/readme.md
@@ -1,5 +1,5 @@
 
-# Xbyak 6.06 [![Badge Build]][Build Status]
+# Xbyak 6.60 [![Badge Build]][Build Status]
 
 *A C++ JIT assembler for x86 (IA32), x64 (AMD64, x86-64)*
 
diff --git a/readme.txt b/readme.txt
index 27f4483..3aecc6b 100644
--- a/readme.txt
+++ b/readme.txt
@@ -1,5 +1,5 @@
 
-    C++用x86(IA-32), x64(AMD64, x86-64) JITアセンブラ Xbyak 6.06
+    C++用x86(IA-32), x64(AMD64, x86-64) JITアセンブラ Xbyak 6.60
 
 -----------------------------------------------------------------------------
 ◎概要
diff --git a/xbyak/xbyak.h b/xbyak/xbyak.h
index f744f29..b0b1947 100644
--- a/xbyak/xbyak.h
+++ b/xbyak/xbyak.h
@@ -144,7 +144,7 @@
 
 enum {
 	DEFAULT_MAX_CODE_SIZE = 4096,
-	VERSION = 0x6060 /* 0xABCD = A.BC(D) */
+	VERSION = 0x6600 /* 0xABCD = A.BC(.D) */
 };
 
 #ifndef MIE_INTEGER_TYPE_DEFINED
diff --git a/xbyak/xbyak_mnemonic.h b/xbyak/xbyak_mnemonic.h
index 57bc44c..88315af 100644
--- a/xbyak/xbyak_mnemonic.h
+++ b/xbyak/xbyak_mnemonic.h
@@ -1,4 +1,4 @@
-const char *getVersionString() const { return "6.06"; }
+const char *getVersionString() const { return "6.60"; }
 void adc(const Operand& op, uint32_t imm) { opRM_I(op, imm, 0x10, 2); }
 void adc(const Operand& op1, const Operand& op2) { opRM_RM(op1, op2, 0x10); }
 void adcx(const Reg32e& reg, const Operand& op) { opGen(reg, op, 0xF6, 0x66, isREG32_REG32orMEM, NONE, 0x38); }