diff --git a/proguard-project.txt b/proguard-project.txt
index 2301761dc..5a9a57a8c 100644
--- a/proguard-project.txt
+++ b/proguard-project.txt
@@ -11,3 +11,9 @@
 # by certain certificates.
 #   Reference: https://gitlab.com/fdroid/fdroidclient/issues/88
 -keep class org.spongycastle.**
+
+# This keeps class members used for SystemInstaller IPC.
+#   Reference: https://gitlab.com/fdroid/fdroidclient/issues/79
+-keepclassmembers class * implements android.os.IInterface {
+    public *;
+}