diff --git a/README.rst b/README.rst
index 43253bef6..6d18f540d 100644
--- a/README.rst
+++ b/README.rst
@@ -77,6 +77,11 @@ Switching build modes in CMake is simple. For debug mode, enter at the command l
 
     cmake -D CMAKE_BUILD_TYPE:String="Debug" .
 
+Note that, with CMake, if you want to change the compiler or its options after you already ran CMake, you need to clear its cache first, eg (using GNU find)::
+
+    find . -iname '*cmake*' -not -name CMakeLists.txt -exec rm -rf {} +
+    CC=gcc CFLAGS='-fstack-protector-strong -Wa,--noexecstack' cmake .
+
 In order to run the tests, enter::
 
     make test
diff --git a/configs/README.txt b/configs/README.txt
index bab500d8d..f543002b7 100644
--- a/configs/README.txt
+++ b/configs/README.txt
@@ -18,7 +18,7 @@ them, you can pick one of the following methods:
 
    Or, using cmake:
 
-    rm CMakeCache.txt
+    find . -iname '*cmake*' -not -name CMakeLists.txt -exec rm -rf {} +
     CFLAGS="-I$PWD/configs -DPOLARSSL_CONFIG_FILE='<foo.h>'" cmake .
     make