diff --git a/lib/bindings/Makefile b/lib/bindings/Makefile
index 171001f..c6d0b2d 100644
--- a/lib/bindings/Makefile
+++ b/lib/bindings/Makefile
@@ -1,4 +1,6 @@
-PKG_CONFIG_PATH := $(shell opam config var prefix)/lib/pkgconfig
+ifneq (, $(shell command -v opam))
+PKG_CONFIG_PATH ?= $(shell opam var prefix)/lib/pkgconfig
+endif
 
 CC ?= cc
 FREESTANDING_CFLAGS := $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH) pkg-config --cflags ocaml-freestanding)
diff --git a/mirage-solo5.opam b/mirage-solo5.opam
index 9eee92a..0173ec8 100644
--- a/mirage-solo5.opam
+++ b/mirage-solo5.opam
@@ -19,7 +19,7 @@ build: [
 depends: [
   "dune" {>= "2.6.0"}
   "bheap" {>= "2.0.0"}
-  "ocaml" {>= "4.06.0"}
+  "ocaml" {>= "4.08.0"}
   "cstruct" {>= "1.0.1"}
   "lwt" {>= "2.4.3"}
   "ocaml-freestanding" {>= "0.4.5"}