diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 9481f2dadab..27e07d21e2e 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -7224,6 +7224,17 @@ init_custom_variable(const char *name,
 		!process_shared_preload_libraries_in_progress)
 		elog(FATAL, "cannot create PGC_POSTMASTER variables after startup");
 
+	/*
+	 * Before pljava commit 398f3b876ed402bdaec8bc804f29e2be95c75139
+	 * (2015-12-15), two of that module's PGC_USERSET variables facilitated
+	 * trivial escalation to superuser privileges.  Restrict the variables to
+	 * protect sites that have yet to upgrade pljava.
+	 */
+	if (context == PGC_USERSET &&
+		(strcmp(name, "pljava.classpath") == 0 ||
+		 strcmp(name, "pljava.vmoptions") == 0))
+		context = PGC_SUSET;
+
 	gen = (struct config_generic *) guc_malloc(ERROR, sz);
 	memset(gen, 0, sz);