diff --git a/.gitignore b/.gitignore
index 38ca1b9..fed45cb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,9 @@
+# OS images are intentionally kept out of git.
+os/*.img
+os/*.img.*
+os/*/*.img
+os/*/*.img.*
+
 # Local audio/debug captures.
 *.wav
 *.aiff