2 files changed, 6 insertions, 1 deletions
diff --git a/src/liballoc_jemalloc/build.rs b/src/liballoc_jemalloc/build.rs
index 18f0527425a..4bc752af48e 100644
--- a/src/liballoc_jemalloc/build.rs
+++ b/src/liballoc_jemalloc/build.rs
@@ -17,6 +17,8 @@ use std::process::Command;
 use build_helper::run;
 
 fn main() {
+    println!("cargo:rustc-cfg=cargobuild");
+
     let target = env::var("TARGET").unwrap();
     let host = env::var("HOST").unwrap();
     let build_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
diff --git a/src/liballoc_jemalloc/lib.rs b/src/liballoc_jemalloc/lib.rs
index d02e9e4ba13..2c46e37ac32 100644
--- a/src/liballoc_jemalloc/lib.rs
+++ b/src/liballoc_jemalloc/lib.rs
@@ -38,7 +38,10 @@ use libc::{c_int, c_void, size_t};
                not(target_os = "android"),
                not(target_env = "musl")),
            link(name = "pthread"))]
-extern "C" {
+#[cfg(not(cargobuild))]
+extern {}
+
+extern {
     fn je_mallocx(size: size_t, flags: c_int) -> *mut c_void;
     fn je_rallocx(ptr: *mut c_void, size: size_t, flags: c_int) -> *mut c_void;
     fn je_xallocx(ptr: *mut c_void, size: size_t, extra: size_t, flags: c_int) -> size_t;