5 files changed, 51 insertions, 4 deletions
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index e5d2fb2ea28..043892410ce 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -110,7 +110,7 @@ pub fn create_session(
     add_configuration(&mut cfg, &mut sess, &*codegen_backend);
 
     let mut check_cfg = config::to_crate_check_config(check_cfg);
-    check_cfg.fill_well_known();
+    check_cfg.fill_well_known(&sess.target);
 
     sess.parse_sess.config = cfg;
     sess.parse_sess.check_config = check_cfg;
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index d4e4ace889b..485c3f55462 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1137,7 +1137,7 @@ impl CrateCheckConfig {
     }
 
     /// Fills a `CrateCheckConfig` with well-known configuration values.
-    fn fill_well_known_values(&mut self) {
+    fn fill_well_known_values(&mut self, current_target: &Target) {
         if !self.well_known_values {
             return;
         }
@@ -1229,6 +1229,7 @@ impl CrateCheckConfig {
             for target in TARGETS
                 .iter()
                 .map(|target| Target::expect_builtin(&TargetTriple::from_triple(target)))
+                .chain(iter::once(current_target.clone()))
             {
                 values_target_os.insert(Symbol::intern(&target.options.os));
                 values_target_family
@@ -1243,9 +1244,9 @@ impl CrateCheckConfig {
         }
     }
 
-    pub fn fill_well_known(&mut self) {
+    pub fn fill_well_known(&mut self, current_target: &Target) {
         self.fill_well_known_names();
-        self.fill_well_known_values();
+        self.fill_well_known_values(current_target);
     }
 }
 
diff --git a/tests/ui/check-cfg/my-awesome-platform.json b/tests/ui/check-cfg/my-awesome-platform.json
new file mode 100644
index 00000000000..5e9ab8f1a2d
--- /dev/null
+++ b/tests/ui/check-cfg/my-awesome-platform.json
@@ -0,0 +1,12 @@
+{
+    "llvm-target": "x86_64-unknown-none-gnu",
+    "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
+    "arch": "x86_64",
+    "target-endian": "little",
+    "target-pointer-width": "64",
+    "target-c-int-width": "32",
+    "os": "ericos",
+    "linker-flavor": "ld.lld",
+    "linker": "rust-lld",
+    "executables": true
+}
diff --git a/tests/ui/check-cfg/values-target-json.rs b/tests/ui/check-cfg/values-target-json.rs
new file mode 100644
index 00000000000..2ef5a44592b
--- /dev/null
+++ b/tests/ui/check-cfg/values-target-json.rs
@@ -0,0 +1,21 @@
+// This test checks that we don't lint values defined by a custom target (target json)
+//
+// check-pass
+// needs-llvm-components: x86
+// compile-flags: --crate-type=lib --check-cfg=values() --target={{src-base}}/check-cfg/my-awesome-platform.json -Z unstable-options
+
+#![feature(lang_items, no_core, auto_traits)]
+#![no_core]
+
+#[lang = "sized"]
+trait Sized {}
+
+#[cfg(target_os = "linuz")]
+//~^ WARNING unexpected `cfg` condition value
+fn target_os_linux_misspell() {}
+
+#[cfg(target_os = "linux")]
+fn target_os_linux() {}
+
+#[cfg(target_os = "ericos")]
+fn target_os_ericos() {}
diff --git a/tests/ui/check-cfg/values-target-json.stderr b/tests/ui/check-cfg/values-target-json.stderr
new file mode 100644
index 00000000000..b58d2970773
--- /dev/null
+++ b/tests/ui/check-cfg/values-target-json.stderr
@@ -0,0 +1,13 @@
+warning: unexpected `cfg` condition value
+  --> $DIR/values-target-json.rs:13:7
+   |
+LL | #[cfg(target_os = "linuz")]
+   |       ^^^^^^^^^^^^-------
+   |                   |
+   |                   help: did you mean: `"linux"`
+   |
+   = note: expected values for `target_os` are: aix, android, cuda, dragonfly, emscripten, ericos, espidf, freebsd, fuchsia, haiku, hermit, horizon, illumos, ios, l4re, linux, macos, netbsd, none, nto, openbsd, psp, redox, solaris, solid_asp3, tvos, uefi, unknown, vita, vxworks, wasi, watchos, windows, xous
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: 1 warning emitted
+