diff --git a/README.rst b/README.rst
index d8d179135b..5b30ee3563 100644
--- a/README.rst
+++ b/README.rst
@@ -94,6 +94,7 @@ Synapse is the reference python/twisted Matrix homeserver implementation.
 System requirements:
 - POSIX-compliant system (tested on Linux & OS X)
 - Python 2.7
+- At least 512 MB RAM.
 
 Synapse is written in python but some of the libraries is uses are written in
 C. So before we can install synapse itself we need a working C compiler and the