Index: src/backend/postmaster/postmaster.c
===================================================================
--- src/backend/postmaster/postmaster.c	(revision 30129)
+++ src/backend/postmaster/postmaster.c	(working copy)
@@ -685,6 +685,9 @@ PostmasterMain(int argc, char *argv[])
 	/* And switch working directory into it */
 	ChangeToDataDir();
 
+	/* Add buffers to accomodate backends "reserved" for autovacuum */
+	NBuffers += autovacuum_max_workers * 2;
+
 	/*
 	 * Check for invalid combinations of GUC settings.
 	 */