diff --git a/amiga/Makefile.defaults b/amiga/Makefile.defaults
index 2134e8373..20022bb98 100644
--- a/amiga/Makefile.defaults
+++ b/amiga/Makefile.defaults
@@ -26,6 +26,10 @@ NETSURF_USE_AMIGA_DATATYPES := YES
 # Valid options: YES, NO
 NETSURF_USE_NSSVG := YES
 
+# Enable building the source object cache filesystem based backing store.
+# Valid options: YES, NO
+NETSURF_FS_BACKING_STORE := YES
+
 # Enable NetSurf's use of Spidermonkey 1.80+
 # Only here to stop the build complaining;
 # enable NETSURF_USE_MOZJS instead for JavaScript support