diff --git a/src/test/ui/feature-gates/feature-gate-const_generics_defaults.rs b/src/test/ui/feature-gates/feature-gate-const_generics_defaults.rs
new file mode 100644
index 00000000000..90959e7a365
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-const_generics_defaults.rs
@@ -0,0 +1,7 @@
+struct A<const N: usize = 3>;
+//~^ ERROR default values for const generic parameters are unstable
+
+fn foo<const N: u8 = 6>() {}
+//~^ ERROR default values for const generic parameters are unstable
+
+fn main() {}
diff --git a/src/test/ui/feature-gates/feature-gate-const_generics_defaults.stderr b/src/test/ui/feature-gates/feature-gate-const_generics_defaults.stderr
new file mode 100644
index 00000000000..00d564772d2
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-const_generics_defaults.stderr
@@ -0,0 +1,18 @@
+error: default values for const generic parameters are unstable
+  --> $DIR/feature-gate-const_generics_defaults.rs:1:27
+   |
+LL | struct A<const N: usize = 3>;
+   |                           ^
+   |
+   = help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
+
+error: default values for const generic parameters are unstable
+  --> $DIR/feature-gate-const_generics_defaults.rs:4:22
+   |
+LL | fn foo<const N: u8 = 6>() {}
+   |                      ^
+   |
+   = help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
+
+error: aborting due to 2 previous errors
+