diff --git a/src/test/run-pass/binops.rs b/src/test/run-pass/binops.rs
index 09743affa79b..365198a0fbca 100644
--- a/src/test/run-pass/binops.rs
+++ b/src/test/run-pass/binops.rs
@@ -116,8 +116,8 @@ fn test_fn() {
 #[abi = "cdecl"]
 #[nolink]
 extern mod test {
-    fn rust_get_sched_id();
-    fn get_task_id();
+    fn rust_get_sched_id() -> libc::intptr_t;
+    fn get_task_id() -> libc::intptr_t;
 }
 
 fn test_foreign_fn() {
diff --git a/src/test/run-pass/c-stack-as-value.rs b/src/test/run-pass/c-stack-as-value.rs
index 0947be381f25..8164913d0f77 100644
--- a/src/test/run-pass/c-stack-as-value.rs
+++ b/src/test/run-pass/c-stack-as-value.rs
@@ -1,6 +1,6 @@
 #[abi = "cdecl"]
 extern mod rustrt {
-    fn get_task_id();
+    fn get_task_id() -> libc::intptr_t;
 }
 
 fn main() {
diff --git a/src/test/run-pass/issue-506.rs b/src/test/run-pass/issue-506.rs
index 565e270baa24..72aff29f9ffe 100644
--- a/src/test/run-pass/issue-506.rs
+++ b/src/test/run-pass/issue-506.rs
@@ -9,7 +9,10 @@ import task;
 
 #[abi = "cdecl"]
 extern mod rustrt {
-    fn get_task_id();
+    fn get_task_id() -> libc::intptr_t;
 }
 
-fn main() { task::spawn(rustrt::get_task_id); }
+fn main() {
+    let f: fn() -> libc::intptr_t = rustrt::get_task_id;
+    task::spawn(unsafe { unsafe::reinterpret_cast(f) });
+}
diff --git a/src/test/run-pass/morestack6.rs b/src/test/run-pass/morestack6.rs
index 5750b9d8c87d..b345679f46d8 100644
--- a/src/test/run-pass/morestack6.rs
+++ b/src/test/run-pass/morestack6.rs
@@ -11,7 +11,7 @@ extern mod rustrt {
     fn rust_get_sched_id() -> libc::intptr_t;
     fn last_os_error() -> ~str;
     fn rust_getcwd() -> ~str;
-    fn get_task_id();
+    fn get_task_id() -> libc::intptr_t;
     fn sched_threads();
     fn rust_get_task();
 }