Fix allocator version

Cargo.toml

diff --git a/Cargo.toml b/Cargo.toml
index 6b78136..53da413 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,7 @@
 
 [dependencies]
 core = { package = "async-support", path = "async-support" }
-linked_list_allocator = { version = "0.6.4", default-features = false }
+linked_list_allocator = { version = "=0.6.5", default-features = false }
 libtock_codegen = { path = "codegen" }
 
 [dev-dependencies]