diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4d7e0b055..a99ca38b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -57,7 +57,8 @@ option(ENABLE_PROGRAMS "Build mbed TLS programs." ON)
 option(UNSAFE_BUILD "Allow unsafe builds. These builds ARE NOT SECURE." OFF)
 option(MBEDTLS_FATAL_WARNINGS "Compiler warnings treated as errors" ON)
 if(CMAKE_HOST_WIN32)
-    option(GEN_FILES "Generate the auto-generated files as needed" OFF)
+    # N.B. The comment on the next line is significant for prepare_release.sh
+    option(GEN_FILES "Generate the auto-generated files as needed" OFF) # off in development
 else()
     option(GEN_FILES "Generate the auto-generated files as needed" ON)
 endif()
diff --git a/scripts/prepare_release.sh b/scripts/prepare_release.sh
index 9013cc878..800383d2c 100755
--- a/scripts/prepare_release.sh
+++ b/scripts/prepare_release.sh
@@ -79,4 +79,4 @@ if [ -n "$unrelease" ]; then
 else
     r='OFF'
 fi
-sed -i 's/^\( *option *( *GEN_FILES  *"[^"]*"  *\)\([A-Za-z0-9][A-Za-z0-9]*\)/\1'"$r/" CMakeLists.txt
+sed -i '/[Oo][Ff][Ff] in development/! s/^\( *option *( *GEN_FILES  *"[^"]*"  *\)\([A-Za-z0-9][A-Za-z0-9]*\)/\1'"$r/" CMakeLists.txt