diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4b3d944acd..a3be86743c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -267,8 +267,7 @@ jobs:
         done
 
   macsimple:
-    # still needs some fix to be upgraded to macos-11
-    runs-on: macos-10.15
+    runs-on: macos-11
     steps:
     - uses: actions/checkout@v2
     - name: Set paths
diff --git a/README.md b/README.md
index 0a79a00156..0e1ea1bf2a 100644
--- a/README.md
+++ b/README.md
@@ -69,7 +69,7 @@ Here's a description of the content of each file and directory in the root PLUME
     Makefile.conf.in : template configuration makefile
     PEOPLE           : list of authors
     README.md        : this file
-    VERSION          : version file
+    VERSION.txt      : version file
     astyle           : a local version of astyle, used to format code
     configure        : configuration script
     configure.ac     : configuration script (autoconf)
diff --git a/VERSION b/VERSION.txt
similarity index 100%
rename from VERSION
rename to VERSION.txt
diff --git a/python/Makefile b/python/Makefile
index 967955d2d0..1ed692191b 100644
--- a/python/Makefile
+++ b/python/Makefile
@@ -3,7 +3,7 @@ ifneq ($(MAKECMDGOALS),clean)
   -include ../Makefile.conf
 endif
 
-VERSION = $(shell if test -f ../VERSION ; then grep -v \\\# ../VERSION ; else echo "Unknown" ; fi )
+VERSION = $(shell if test -f ../VERSION.txt ; then grep -v \\\# ../VERSION.txt ; else echo "Unknown" ; fi )
 
 .PHONY: all clean install
 
@@ -29,7 +29,7 @@ all:
 endif
 
 pip:
-	cp ../VERSION ./PLUMED_VERSION
+	cp ../VERSION.txt ./PLUMED_VERSION
 	mkdir -p include
 	cp ../src/wrapper/Plumed.h include/
 
@@ -45,6 +45,6 @@ pypi:
 	cp -r test pypi/
 	cp ../src/wrapper/Plumed.h pypi/include/
 	cp README.rst MANIFEST.in cplumed.pxd plumed.pyx setup.py pypi/
-	cp ../VERSION pypi/PLUMED_VERSION
+	cp ../VERSION.txt pypi/PLUMED_VERSION
 	cd pypi ; $(python_bin) setup.py sdist
 	echo "now use: $(python_bin) -m twine upload dist/plumed-$(VERSION).tar.gz"
diff --git a/python/setup.py b/python/setup.py
index cd3b30e83d..3ddb112316 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -40,7 +40,7 @@ def is_platform_mac():
     return sys.platform == 'darwin'
 
 if os.getenv("plumed_macports") is not None:
-    copyfile("../VERSION","PLUMED_VERSION")
+    copyfile("../VERSION.txt","PLUMED_VERSION")
     try:
         os.mkdir("include")
     except OSError:
diff --git a/release.sh b/release.sh
index 8c0cdeb4a9..17e80c4a99 100755
--- a/release.sh
+++ b/release.sh
@@ -137,13 +137,13 @@ if ! test "$VALIDATED" ; then
 else
   update_changelog CHANGES/v$shortversion.md $version $shortversion "$(date '+%b %e, %Y' | sed 's/  / /g')"
   {
-    grep  \# VERSION 
+    grep  \# VERSION.txt 
     echo $version
   } > VERSION.tmp
-  mv VERSION.tmp VERSION
+  mv VERSION.tmp VERSION.txt
   echo "Here's the new VERSION file:"
   echo "***"
-  cat VERSION
+  cat VERSION.txt
   echo "***"
   msg="Release v$version
 "
@@ -152,7 +152,7 @@ else
   echo "I will use the following commands:"
   echo "***"
   echo "git add CHANGES/v$shortversion.md"
-  echo "git add VERSION"
+  echo "git add VERSION.txt"
   echo "git commit --allow-empty -m \"$msg\""
   echo "git tag v$version"
   echo "git push origin v$version"
@@ -160,7 +160,7 @@ else
   echo "***"
   confirm || exit
   git add CHANGES/v$shortversion.md
-  git add VERSION
+  git add VERSION.txt
   git commit --allow-empty -m "$msg"
   git tag v$version
   git push origin v$shortversion v$version
diff --git a/src/lib/Makefile b/src/lib/Makefile
index b808e0b33a..a64a2ca54e 100644
--- a/src/lib/Makefile
+++ b/src/lib/Makefile
@@ -1,6 +1,6 @@
 
 # version number
-VERSION = $(shell if test -f ../../VERSION ; then grep -v \\\# ../../VERSION ; else echo "Unknown" ; fi )
+VERSION = $(shell if test -f ../../VERSION.txt ; then grep -v \\\# ../../VERSION.txt ; else echo "Unknown" ; fi )
 
 # here we build the list of modules to be linked in plumedKernel
 KERNEL_MODULES := $(addprefix ../,$(shell ../maketools/find_modules.sh))
diff --git a/src/maketools/update-config-txt.sh b/src/maketools/update-config-txt.sh
index 48f4bd59c6..198750e188 100755
--- a/src/maketools/update-config-txt.sh
+++ b/src/maketools/update-config-txt.sh
@@ -6,16 +6,16 @@ file="$1"
 # version strings:
 version=$(
 echo "version short $(
-  if test -f ../../VERSION ; then
-    grep -v "#" ../../VERSION | sed  's/^\([0-9][0-9]*\.[0-9][0-9]*\).*/\1/'
+  if test -f ../../VERSION.txt ; then
+    grep -v "#" ../../VERSION.txt | sed  's/^\([0-9][0-9]*\.[0-9][0-9]*\).*/\1/'
   else
     echo "Unknown"
   fi
 )"
 
 echo "version long $(
-  if test -f ../../VERSION ; then
-    grep -v "#" ../../VERSION
+  if test -f ../../VERSION.txt ; then
+    grep -v "#" ../../VERSION.txt
   else
     echo "Unknown"
   fi
diff --git a/src/maketools/update-version.sh b/src/maketools/update-version.sh
index 9016ec7ab7..09cf4013ae 100755
--- a/src/maketools/update-version.sh
+++ b/src/maketools/update-version.sh
@@ -4,16 +4,16 @@
 echo "#ifndef __PLUMED_config_version_h"
 echo "#define __PLUMED_config_version_h"
 echo "#define PLUMED_VERSION_SHORT \"$(
-  if test -f ../../VERSION ; then
-    grep -v "#" ../../VERSION | sed  's/^\([0-9][0-9]*\.[0-9][0-9]*\).*/\1/'
+  if test -f ../../VERSION.txt ; then
+    grep -v "#" ../../VERSION.txt | sed  's/^\([0-9][0-9]*\.[0-9][0-9]*\).*/\1/'
   else
     echo "Unknown"
   fi
 )\""
 
 echo "#define PLUMED_VERSION_LONG \"$(
-  if test -f ../../VERSION ; then
-    grep -v "#" ../../VERSION
+  if test -f ../../VERSION.txt ; then
+    grep -v "#" ../../VERSION.txt
   else
     echo "Unknown"
   fi
@@ -29,15 +29,15 @@ echo "#define PLUMED_VERSION_GIT \"$(
 )\""
 
 echo "#define PLUMED_VERSION_MAJOR $(
-  grep -v "#" ../../VERSION | sed  's/^\([0-9][0-9]*\).*/\1/'
+  grep -v "#" ../../VERSION.txt | sed  's/^\([0-9][0-9]*\).*/\1/'
 )"
 
 echo "#define PLUMED_VERSION_MINOR $(
-  grep -v "#" ../../VERSION | sed  's/^[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/'
+  grep -v "#" ../../VERSION.txt | sed  's/^[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/'
 )"
 
 echo "#define PLUMED_VERSION_PATCH $(
-  grep -v "#" ../../VERSION | sed  's/^[0-9][0-9]*\.[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/'
+  grep -v "#" ../../VERSION.txt | sed  's/^[0-9][0-9]*\.[0-9][0-9]*\.\([0-9][0-9]*\).*/\1/'
 )"
 
 echo "#endif"