diff --git a/src/librustc_trans/back/write.rs b/src/librustc_trans/back/write.rs
index de21d6265149..488a4a8082f9 100644
--- a/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@ -348,7 +348,7 @@ unsafe extern "C" fn report_inline_asm<'a, 'b>(cgcx: &'a CodegenContext<'a>,
 
     match cgcx.lto_ctxt {
         Some((sess, _)) => {
-            sess.codemap().with_expn_info(ExpnId::from_llvm_cookie(cookie), |info| match info {
+            sess.codemap().with_expn_info(ExpnId::from_u32(cookie), |info| match info {
                 Some(ei) => sess.span_err(ei.call_site, msg),
                 None     => sess.err(msg),
             });
diff --git a/src/librustc_trans/trans/asm.rs b/src/librustc_trans/trans/asm.rs
index d6c85e8b1734..27128827e267 100644
--- a/src/librustc_trans/trans/asm.rs
+++ b/src/librustc_trans/trans/asm.rs
@@ -138,7 +138,7 @@ pub fn trans_inline_asm<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, ia: &ast::InlineAsm)
         let kind = llvm::LLVMGetMDKindIDInContext(bcx.ccx().llcx(),
             key.as_ptr() as *const c_char, key.len() as c_uint);
 
-        let val: llvm::ValueRef = C_i32(bcx.ccx(), ia.expn_id.to_llvm_cookie());
+        let val: llvm::ValueRef = C_i32(bcx.ccx(), ia.expn_id.into_u32() as i32);
 
         llvm::LLVMSetMetadata(r, kind,
             llvm::LLVMMDNodeInContext(bcx.ccx().llcx(), &val, 1));
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 6acc56fb41aa..a0c29a2371b4 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -26,7 +26,6 @@ use std::rc::Rc;
 
 use std::fmt;
 
-use libc::c_uint;
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 
 
@@ -287,13 +286,12 @@ pub const NO_EXPANSION: ExpnId = ExpnId(!0);
 pub const COMMAND_LINE_EXPN: ExpnId = ExpnId(!1);
 
 impl ExpnId {
-    pub fn from_llvm_cookie(cookie: c_uint) -> ExpnId {
-        ExpnId(cookie)
+    pub fn from_u32(id: u32) -> ExpnId {
+        ExpnId(id)
     }
 
-    pub fn to_llvm_cookie(self) -> i32 {
-        let ExpnId(cookie) = self;
-        cookie as i32
+    pub fn into_u32(self) -> u32 {
+        self.0
     }
 }