diff --git a/src/consts.rs b/src/consts.rs
index 05cec2ca..da809793 100644
--- a/src/consts.rs
+++ b/src/consts.rs
@@ -28,17 +28,3 @@ pub const UHYVE_QUEUE_SIZE: usize = 8;
 pub const UHYVE_IRQ_NET: u32 = 11;
 
 pub const GUEST_PAGE_SIZE: u64 = 0x200000; /* 2 MB pages in guest */
-
-// File operations supported by Hermit and Uhyve
-pub const O_RDONLY: i32 = 0o0000;
-pub const O_WRONLY: i32 = 0o0001;
-pub const O_RDWR: i32 = 0o0002;
-pub const O_CREAT: i32 = 0o0100;
-pub const O_EXCL: i32 = 0o0200;
-pub const O_TRUNC: i32 = 0o1000;
-pub const O_APPEND: i32 = 0o2000;
-pub const O_DIRECT: i32 = 0o40000;
-pub const O_DIRECTORY: i32 = 0o200000;
-
-pub const ALLOWED_OPEN_FLAGS: i32 =
-	O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_TRUNC | O_APPEND | O_DIRECT | O_DIRECTORY;
diff --git a/src/hypercall.rs b/src/hypercall.rs
index f8f6cb6c..18548f21 100644
--- a/src/hypercall.rs
+++ b/src/hypercall.rs
@@ -4,11 +4,12 @@ use std::{
 	os::unix::ffi::OsStrExt,
 };
 
+use libc::{EINVAL, EIO, ENOENT};
 use tempfile::TempDir;
 use uhyve_interface::{parameters::*, GuestPhysAddr, Hypercall, HypercallAddress, MAX_ARGC_ENVC};
 
 use crate::{
-	consts::{ALLOWED_OPEN_FLAGS, BOOT_PML4, O_CREAT, O_DIRECTORY, O_EXCL},
+	consts::BOOT_PML4,
 	isolation::UhyveFileMap,
 	mem::{MemoryError, MmapMemory},
 	virt_to_phys,
@@ -97,11 +98,11 @@ pub fn unlink(mem: &MmapMemory, sysunlink: &mut UnlinkParams, file_map: &mut Uhy
 			}
 		} else {
 			error!("The kernel requested to unlink() an unknown path ({guest_path}): Rejecting...");
-			sysunlink.ret = -1;
+			sysunlink.ret = -ENOENT;
 		}
 	} else {
 		error!("The kernel requested to open() a path that is not valid UTF-8. Rejecting...");
-		sysunlink.ret = -1;
+		sysunlink.ret = -EIO;
 	}
 }
 
@@ -142,7 +143,7 @@ pub fn open(
 			// See: https://github.com/hermit-os/kernel/commit/71bc629
 			if (flags & (O_DIRECTORY | O_CREAT)) == (O_DIRECTORY | O_CREAT) {
 				error!("An open() call used O_DIRECTORY and O_CREAT at the same time. Aborting...");
-				sysopen.ret = -1
+				sysopen.ret = -EINVAL
 			}
 
 			// Existing files that already exist should be in the file map, not here.
@@ -162,7 +163,7 @@ pub fn open(
 		}
 	} else {
 		error!("The kernel requested to open() a path that is not valid UTF-8. Rejecting...");
-		sysopen.ret = -1;
+		sysopen.ret = -EINVAL;
 	}
 }
 
diff --git a/uhyve-interface/src/parameters.rs b/uhyve-interface/src/parameters.rs
index e255ae08..70638247 100644
--- a/uhyve-interface/src/parameters.rs
+++ b/uhyve-interface/src/parameters.rs
@@ -144,3 +144,17 @@ pub struct SerialWriteBufferParams {
 	pub buf: GuestPhysAddr,
 	pub len: usize,
 }
+
+// File operations supported by Hermit and Uhyve
+pub const O_RDONLY: i32 = 0o0000;
+pub const O_WRONLY: i32 = 0o0001;
+pub const O_RDWR: i32 = 0o0002;
+pub const O_CREAT: i32 = 0o0100;
+pub const O_EXCL: i32 = 0o0200;
+pub const O_TRUNC: i32 = 0o1000;
+pub const O_APPEND: i32 = 0o2000;
+pub const O_DIRECT: i32 = 0o40000;
+pub const O_DIRECTORY: i32 = 0o200000;
+
+pub const ALLOWED_OPEN_FLAGS: i32 =
+	O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_TRUNC | O_APPEND | O_DIRECT | O_DIRECTORY;