diff --git a/.cirrus.yml b/.cirrus.yml
index 3578fb7..9c826d9 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -1,16 +1,17 @@
 task:
-  name: Linux gcc 5/9/latest builds
+  name: Linux gcc 9/11/latest builds
   skip: "changesIncludeOnly('docs/*')"
   env:
     CIRRUS_CLONE_DEPTH: 1
     CIRRUS_CLONE_SUBMODULES: true
   container:
     matrix:
-      image: gcc:5
       image: gcc:9
+      image: gcc:11
       image: gcc:latest
     cpu: 2
     memory: 1G
+  gcc_version_script: gcc --version
   build_script: make clean && make -j3
   install_script: make install && make clean
   ## now try the built+installed sjasmplus with some tests and examples
@@ -41,9 +42,7 @@ pipe:
     cpu: 2
     memory: 1G
   steps:
-    # demoted back to gcc6 because gcov+lcov in gcc:8 and 9 image seems to produce a bit damaged coverage results?
-    # (I didn't dig into the issue, just trying to change version back to where it works well)
-    - image: gcc:6
+    - image: gcc:11
       generate_gcov_script: make clean && make -j3 coverage
     - image: python:3.7
       # installing my patched version of "cpp-coveralls" to get support for CI_SERVICE_NAME and git-revision number
@@ -121,15 +120,13 @@ task:
     CIRRUS_CLONE_DEPTH: 1
     CIRRUS_CLONE_SUBMODULES: true
   macos_instance:
-    #image: big-sur-base
-    image: ghcr.io/cirruslabs/macos-monterey-base:latest
-  #sw_versions2_script:
-    #- git --version || echo "no git"
-    #- bash --version || echo "no bash"
-    #- make --version || echo "no make"
-    #- cc --version || echo "no cc"
-    #- c++ --version || echo "no c++"
-  build_script:
+    image: ghcr.io/cirruslabs/macos-sonoma-base:latest
+  sw_versions2_script:
+    - git --version || echo "no git"
+    - bash --version || echo "no bash"
+    - make --version || echo "no make"
+    - cc --version || echo "no cc"
+    - c++ --version || echo "no c++"
     - date
-    - make clean && make -j10 CC=cc CXX=c++
+  build_script: make clean && make -j10 CC=cc CXX=c++
   test_script: make clean && make -j10 CC=cc CXX=c++ tests
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 286d1b0..a28bf5b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,9 +39,9 @@ set(SOURCES
 add_definitions(-DMAX_PATH=PATH_MAX)
 add_definitions(-DCMAKE)
 
-set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
-set(CMAKE_CXX_EXTENSIONS ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
 
 set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -Wall -pedantic")
 set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -Wall -pedantic")
diff --git a/INSTALL.md b/INSTALL.md
index 91b92b5..75fdfb7 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -13,7 +13,7 @@ or
 - complete MinGW environment for MS Windows, configured with MinGW bin directories added in `PATH` variable (typically `C:\MinGW\bin;` `C:\MinGW\msys\1.0\bin`) or possibly with any BASH emulator (e.g. the one which comes with [git for windows](https://gitforwindows.org/)) will do it instead of msys is missing / not set.
 - CMake installed into MinGW bin directory (optionally)
 
-Compilation is tested with GCC 5.5.0, it should run also with older 5.x versions. It will not work with GCC 4.x and older.
+C++17 standard is required, compilation is tested with GCC 9.5.0, it should run also with older 9.x versions. It will not work with GCC 8.x and older. C++17 is required since v1.21.0, older versions required C++14 and can be built with GCC 5.x.
 
 ## Getting full source code of sjasmplus
 
diff --git a/Makefile b/Makefile
index eedb51b..ab0f05b 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@
 # make tests 					- to run the CI test+example script runner
 # make memcheck TEST=misc DEBUG=1		- to use valgrind on assembling sub-directory "misc" in tests
 # make PREFIX=~/.local install			- to install release version into ~/.local/bin/
-# make clean && make CC=gcc-8 CXX=g++-8		- to compile binary with gcc-8
+# make clean && make CC=gcc-9 CXX=g++-9		- to compile binary with gcc-9
 # make DEBUG=1 LUA_COVERAGE=1 coverage		- to produce build/debug/coverage/* files by running the tests
 # make COVERALLS_SERVICE=1 DEBUG=1 coverage	- to produce coverage data and upload them to https://coveralls.io/
 # make CFLAGS_EXTRA='-m32' LDFLAGS='-ldl -m32'  - to builds 32b linux executable
@@ -103,7 +103,7 @@ CFLAGS+=-DNDEBUG -O2
 endif
 
 # C++ flags (the CPPFLAGS are for preprocessor BTW, if you always wonder, like me...)
-CXXFLAGS?=-std=gnu++14 $(CFLAGS)
+CXXFLAGS?=-std=c++17 $(CFLAGS)
 
 # full path to executable
 BUILD_EXE=$(BUILD_DIR)/$(EXE_BASE_NAME)
diff --git a/Makefile.win b/Makefile.win
index b924cbe..0a6bf71 100644
--- a/Makefile.win
+++ b/Makefile.win
@@ -26,7 +26,7 @@ SUBDIR_CRC32C=crc32c
 
 # Ped7g: -pedantic removed due to Lua5.4 having too many warnings
 CFLAGS=-DNDEBUG -O2 -Wall -static -DUSE_LUA -DMAX_PATH=PATH_MAX -I$(SUBDIR_LUA) -I$(SUBDIR_LUABRIDGE) -I$(SUBDIR_CRC32C)
-CXXFLAGS=-std=gnu++14 $(CFLAGS)
+CXXFLAGS=-std=c++17 $(CFLAGS)
 
 LDFLAGS= -s
 
diff --git a/docs/documentation.xml b/docs/documentation.xml
index 111be0d..4eeab99 100644
--- a/docs/documentation.xml
+++ b/docs/documentation.xml
@@ -208,6 +208,7 @@
 
             <listitem>
               <synopsis>
+- C++17 standard is now required minimum (to compile sjasmplus sources) (GCC9 for example)
 - <link linkend="po_incbin">`INCBIN`</link>, <link linkend="po_inchob">`INCHOB`</link> and <link linkend="po_inctrd">`INCTRD`</link> support now include paths priority (angle &lt;filename&gt; vs "filename")
 - include paths which can't be opened before assembling are now reported in error message
 - include paths which start with literal tilde '~' are reported in error message