diff --git a/.gitignore b/.gitignore
index a04f5bc..b794da1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,10 @@ play-service-account*.json
 # Gradle and Android build output
 .gradle/
 build/
+# Eclipse/Buildship writes duplicate sources here for the pure-JVM modules. It
+# is build output that looks exactly like source, and it slipped into a commit
+# once before this line existed.
+bin/
 captures/
 .cxx/
 *.apk