diff --git a/Readme.md b/Readme.md
index 68fb5b6353..96257e00ac 100644
--- a/Readme.md
+++ b/Readme.md
@@ -41,6 +41,12 @@ and tests there.
 
 We even run Travis tests for SassC!
 
+### DEBUG builds
+
+Set the environment variable `DEBUG` to `1` to enable debug builds that can be debugged
+with `gdb`, `lldb` and others. E.g.: use `$ DEBUG=1 ./script/spec` to run the tests with
+a debug build.
+
 Tests
 -------