diff --git a/src/bin/miri.rs b/src/bin/miri.rs
index c2255d706339..d8d7cfe0702e 100644
--- a/src/bin/miri.rs
+++ b/src/bin/miri.rs
@@ -154,6 +154,14 @@ fn init_late_loggers() {
             rustc_driver::init_rustc_env_logger();
         }
     }
+
+    // If MIRI_BACKTRACE is set and RUST_CTFE_BACKTRACE is not, set RUST_CTFE_BACKTRACE.
+    // Do this late, so we really only apply this to miri's errors.
+    if let Ok(var) = env::var("MIRI_BACKTRACE") {
+        if env::var("RUST_CTFE_BACKTRACE") == Err(env::VarError::NotPresent) {
+            env::set_var("RUST_CTFE_BACKTRACE", &var);
+        }
+    }
 }
 
 fn find_sysroot() -> String {
diff --git a/src/lib.rs b/src/lib.rs
index 7643f93fdc2c..bb6c9e3ca503 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,7 +15,6 @@ extern crate rustc_target;
 
 use std::collections::HashMap;
 use std::borrow::Cow;
-use std::env;
 
 use rustc::ty::{self, TyCtxt, query::TyCtxtAt};
 use rustc::ty::layout::{TyLayout, LayoutOf, Size, Align};
@@ -184,14 +183,6 @@ pub fn eval_main<'a, 'tcx: 'a>(
 ) {
     let mut ecx = create_ecx(tcx, main_id, validate).expect("Couldn't create ecx");
 
-    // If MIRI_BACKTRACE is set and RUST_CTFE_BACKTRACE is not, set RUST_CTFE_BACKTRACE.
-    // Do this late, so we really only apply this to miri's errors.
-    if let Ok(var) = env::var("MIRI_BACKTRACE") {
-        if env::var("RUST_CTFE_BACKTRACE") == Err(env::VarError::NotPresent) {
-            env::set_var("RUST_CTFE_BACKTRACE", &var);
-        }
-    }
-
     // Run! The main execution.
     let res: EvalResult = (|| {
         ecx.run()?;