diff --git a/include/perk/perk.h b/include/perk/perk.h
index 9e4b035..451b37e 100644
--- a/include/perk/perk.h
+++ b/include/perk/perk.h
@@ -153,7 +153,7 @@ struct pe_unit_ctx {
 perk_api int  pe_get_driver_ctx		(const char ** argv, const char ** envp, uint32_t flags, struct pe_driver_ctx **);
 perk_api void pe_free_driver_ctx	(struct pe_driver_ctx *);
 
-perk_api int  pe_get_unit_ctx		(struct pe_driver_ctx *, const char * path, struct pe_unit_ctx **);
+perk_api int  pe_get_unit_ctx		(const struct pe_driver_ctx *, const char * path, struct pe_unit_ctx **);
 perk_api void pe_free_unit_ctx		(struct pe_unit_ctx *);
 
 /* utility api */
diff --git a/src/driver/pe_unit_ctx.c b/src/driver/pe_unit_ctx.c
index 77b74bc..e542681 100644
--- a/src/driver/pe_unit_ctx.c
+++ b/src/driver/pe_unit_ctx.c
@@ -19,9 +19,9 @@ static int pe_free_unit_ctx_impl(struct pe_unit_ctx_impl * ctx, int status)
 }
 
 int pe_get_unit_ctx(
-	struct pe_driver_ctx *	dctx,
-	const char *		path,
-	struct pe_unit_ctx **	pctx)
+	const struct pe_driver_ctx *	dctx,
+	const char *			path,
+	struct pe_unit_ctx **		pctx)
 {
 	struct pe_unit_ctx_impl *	ctx;
 	int			prot;