diff --git a/artiq/firmware/libbacktrace_artiq/lib.rs b/artiq/firmware/libbacktrace_artiq/lib.rs
index cf06c8f5a..7e84e5e44 100644
--- a/artiq/firmware/libbacktrace_artiq/lib.rs
+++ b/artiq/firmware/libbacktrace_artiq/lib.rs
@@ -1,5 +1,4 @@
-#![feature(libc, panic_unwind, never_type)]
-#![allow(non_upper_case_globals, non_camel_case_types)]
+#![feature(libc, panic_unwind)]
 #![no_std]
 
 extern crate unwind;
@@ -8,13 +7,6 @@ extern crate libc;
 use unwind as uw;
 use libc::c_void;
 
-type _Unwind_Trace_Fn = extern "C" fn(*mut uw::_Unwind_Context, *mut c_void)
-                                     -> uw::_Unwind_Reason_Code;
-extern {
-    fn _Unwind_Backtrace(trace_fn: _Unwind_Trace_Fn, arg: *mut c_void)
-                        -> uw::_Unwind_Reason_Code;
-}
-
 pub fn backtrace<F>(mut f: F) -> Result<(), uw::_Unwind_Reason_Code>
     where F: FnMut(usize) -> ()
 {
@@ -30,7 +22,7 @@ pub fn backtrace<F>(mut f: F) -> Result<(), uw::_Unwind_Reason_Code>
     }
 
     unsafe {
-        match _Unwind_Backtrace(trace::<F>, &mut f as *mut _ as *mut c_void) {
+        match uw::_Unwind_Backtrace(trace::<F>, &mut f as *mut _ as *mut c_void) {
             uw::_URC_NO_REASON => Ok(()),
             err => Err(err)
         }
diff --git a/artiq/firmware/runtime/Makefile b/artiq/firmware/runtime/Makefile
index aa2e43b6f..187793ae4 100644
--- a/artiq/firmware/runtime/Makefile
+++ b/artiq/firmware/runtime/Makefile
@@ -6,7 +6,6 @@ CFLAGS += \
 	-I$(LIBUNWIND_DIRECTORY)/../unwinder/include \
 
 LDFLAGS += -L../libbase \
-	-L../libprintf \
 	-L../libunwind
 
 RUSTFLAGS += -Cpanic=abort
@@ -19,7 +18,7 @@ $(RUSTOUT)/libruntime.a:
 
 runtime.elf: $(RUSTOUT)/libruntime.a ksupport_data.o
 	$(LD) $(LDFLAGS) -T $(RUNTIME_DIRECTORY)/runtime.ld -o $@ $^ \
-		-lunwind-bare -lprintf-nofloat --eh-frame-hdr
+		-lunwind-bare
 	@chmod -x $@
 
 ksupport_data.o: ../ksupport/ksupport.elf