diff --git a/crates/private/support/sel4-simple-task/runtime/src/lib.rs b/crates/private/support/sel4-simple-task/runtime/src/lib.rs
index 4c7a6b051..e893590c0 100644
--- a/crates/private/support/sel4-simple-task/runtime/src/lib.rs
+++ b/crates/private/support/sel4-simple-task/runtime/src/lib.rs
@@ -12,7 +12,6 @@
 #[cfg(feature = "alloc")]
 extern crate alloc;
 
-use core::ffi::c_char;
 use core::ptr;
 use core::slice;
 
@@ -122,11 +121,7 @@ fn abort_hook(info: Option<&AbortInfo>) {
 
 sel4_panicking_env::register_abort_hook!(abort_hook);
 
-fn debug_put_char(c: u8) {
-    sel4::debug_put_char(c as c_char)
-}
-
-sel4_panicking_env::register_debug_put_char!(debug_put_char);
+sel4_panicking_env::register_debug_put_char!(sel4::debug_put_char);
 
 fn panic_hook(info: &ExternalPanicInfo<'_>) {
     debug_println!("{}", info);
diff --git a/crates/sel4-microkit/src/panicking.rs b/crates/sel4-microkit/src/panicking.rs
index 24efb1d9e..5b9156ac0 100644
--- a/crates/sel4-microkit/src/panicking.rs
+++ b/crates/sel4-microkit/src/panicking.rs
@@ -43,7 +43,7 @@ pub(crate) fn init_panicking() {
 fn debug_put_char(c: u8) {
     sel4::sel4_cfg_if! {
         if #[cfg(PRINTING)] {
-            sel4::debug_put_char(c as core::ffi::c_char)
+            sel4::debug_put_char(c)
         }
     }
 }
diff --git a/crates/sel4-newlib/src/lib.rs b/crates/sel4-newlib/src/lib.rs
index 4e85e0681..c2502dc03 100644
--- a/crates/sel4-newlib/src/lib.rs
+++ b/crates/sel4-newlib/src/lib.rs
@@ -53,8 +53,8 @@ mod impl_write {
             1 | 2 => {
                 let bytes =
                     unsafe { slice::from_raw_parts(ptr.cast::<u8>(), len.try_into().unwrap()) };
-                for b in bytes {
-                    debug_put_char(*b);
+                for &b in bytes {
+                    debug_put_char(b);
                 }
                 len
             }
diff --git a/crates/sel4-root-task/src/lib.rs b/crates/sel4-root-task/src/lib.rs
index db3d80b68..622fade34 100644
--- a/crates/sel4-root-task/src/lib.rs
+++ b/crates/sel4-root-task/src/lib.rs
@@ -8,7 +8,6 @@
 #![feature(cfg_target_thread_local)]
 #![feature(never_type)]
 
-use core::ffi::c_char;
 use core::fmt;
 
 pub use sel4_panicking_env::{abort, debug_print, debug_println};
@@ -83,11 +82,7 @@ where
     }
 }
 
-fn debug_put_char(c: u8) {
-    sel4::debug_put_char(c as c_char)
-}
-
-sel4_panicking_env::register_debug_put_char!(debug_put_char);
+sel4_panicking_env::register_debug_put_char!(sel4::debug_put_char);
 
 #[macro_export]
 macro_rules! declare_root_task {
diff --git a/crates/sel4/src/debug.rs b/crates/sel4/src/debug.rs
index ba8eb5070..b846ad597 100644
--- a/crates/sel4/src/debug.rs
+++ b/crates/sel4/src/debug.rs
@@ -5,12 +5,10 @@
 // SPDX-License-Identifier: MIT
 //
 
-use core::ffi::c_char;
-
 use crate::{sys, InvocationContext, CapType, TCB, LocalCPtr};
 
 /// Corresponds to `seL4_DebugPutChar`.
-pub fn debug_put_char(c: c_char) {
+pub fn debug_put_char(c: u8) {
     sys::seL4_DebugPutChar(c)
 }
 
diff --git a/crates/sel4/src/fmt.rs b/crates/sel4/src/fmt.rs
index 98d47ed0d..a4ca4e708 100644
--- a/crates/sel4/src/fmt.rs
+++ b/crates/sel4/src/fmt.rs
@@ -5,7 +5,6 @@
 // SPDX-License-Identifier: MIT
 //
 
-use core::ffi::c_char;
 use core::fmt;
 
 use crate::debug_put_char;
@@ -21,7 +20,7 @@ pub struct DebugWrite;
 impl fmt::Write for DebugWrite {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         for &c in s.as_bytes() {
-            debug_put_char(c as c_char)
+            debug_put_char(c)
         }
         Ok(())
     }
diff --git a/crates/sel4/sys/src/syscalls/calls.rs b/crates/sel4/sys/src/syscalls/calls.rs
index c19aa4a38..728bf4206 100644
--- a/crates/sel4/sys/src/syscalls/calls.rs
+++ b/crates/sel4/sys/src/syscalls/calls.rs
@@ -4,7 +4,7 @@
 // SPDX-License-Identifier: BSD-2-Clause
 //
 
-use core::ffi::{c_char, c_int};
+use core::ffi::c_int;
 use core::sync::atomic::{compiler_fence, Ordering};
 
 use sel4_config::{sel4_cfg, sel4_cfg_if};
@@ -631,7 +631,7 @@ pub fn seL4_Yield() {
 
 sel4_cfg_if! {
     if #[cfg(DEBUG_BUILD)] {
-        pub fn seL4_DebugPutChar(c: c_char) {
+        pub fn seL4_DebugPutChar(c: u8) {
             sys_send_recv_simple(syscall_id::DebugPutChar, c as seL4_Word);
         }
 
diff --git a/crates/sel4/sys/src/wrappers/syscalls.rs b/crates/sel4/sys/src/wrappers/syscalls.rs
index f1565fcc8..cf450463f 100644
--- a/crates/sel4/sys/src/wrappers/syscalls.rs
+++ b/crates/sel4/sys/src/wrappers/syscalls.rs
@@ -385,9 +385,11 @@ pub unsafe extern "C" fn seL4_Poll(src: seL4_CPtr, sender: *mut seL4_Word) -> se
 
 sel4_cfg_if! {
     if #[cfg(DEBUG_BUILD)] {
+        // Doesn't actually matter, but libsel4 uses char, which may be signed. Use c_char here and
+        // cast to u8 for the sake of principles.
         #[no_mangle]
         pub unsafe extern "C" fn seL4_DebugPutChar(c: c_char) {
-            crate::seL4_DebugPutChar(c)
+            crate::seL4_DebugPutChar(c as u8)
         }
 
         #[no_mangle]
diff --git a/crates/sel4/sys/wrappers/src/panic_handler.rs b/crates/sel4/sys/wrappers/src/panic_handler.rs
index 1bc0ba3fc..ec9a04d70 100644
--- a/crates/sel4/sys/wrappers/src/panic_handler.rs
+++ b/crates/sel4/sys/wrappers/src/panic_handler.rs
@@ -4,7 +4,6 @@
 // SPDX-License-Identifier: BSD-2-Clause
 //
 
-use core::ffi::c_char;
 use core::fmt::{self, Write};
 use core::panic::PanicInfo;
 
@@ -21,7 +20,7 @@ struct Debug;
 impl Write for Debug {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         for &c in s.as_bytes() {
-            seL4_DebugPutChar(c as c_char)
+            seL4_DebugPutChar(c)
         }
         Ok(())
     }