diff --git a/src/librustc_builtin_macros/assert.rs b/src/librustc_builtin_macros/assert.rs
index 5da4a540940c2..09ff770e87b59 100644
--- a/src/librustc_builtin_macros/assert.rs
+++ b/src/librustc_builtin_macros/assert.rs
@@ -80,17 +80,15 @@ fn parse_assert<'a>(
     //     my_function();
     // );
     //
-    // Warn about semicolon and suggest removing it. Eventually, this should be turned into an
-    // error.
+    // Emit an error about semicolon and suggest removing it.
     if parser.token == token::Semi {
-        let mut err = cx.struct_span_warn(sp, "macro requires an expression as an argument");
+        let mut err = cx.struct_span_err(sp, "macro requires an expression as an argument");
         err.span_suggestion(
             parser.token.span,
             "try removing semicolon",
             String::new(),
             Applicability::MaybeIncorrect,
         );
-        err.note("this is going to be an error in the future");
         err.emit();
 
         parser.bump();
@@ -101,11 +99,10 @@ fn parse_assert<'a>(
     //
     // assert!(true "error message");
     //
-    // Parse this as an actual message, and suggest inserting a comma. Eventually, this should be
-    // turned into an error.
+    // Emit an error and suggest inserting a comma.
     let custom_message =
         if let token::Literal(token::Lit { kind: token::Str, .. }) = parser.token.kind {
-            let mut err = cx.struct_span_warn(parser.token.span, "unexpected string literal");
+            let mut err = cx.struct_span_err(parser.token.span, "unexpected string literal");
             let comma_span = parser.prev_token.span.shrink_to_hi();
             err.span_suggestion_short(
                 comma_span,
@@ -113,7 +110,6 @@ fn parse_assert<'a>(
                 ", ".to_string(),
                 Applicability::MaybeIncorrect,
             );
-            err.note("this is going to be an error in the future");
             err.emit();
 
             parse_custom_message(&mut parser)
diff --git a/src/test/ui/macros/assert-trailing-junk.rs b/src/test/ui/macros/assert-trailing-junk.rs
index 676ae05bf0fa6..cd7faf9bf8bfb 100644
--- a/src/test/ui/macros/assert-trailing-junk.rs
+++ b/src/test/ui/macros/assert-trailing-junk.rs
@@ -13,12 +13,12 @@ fn main() {
     //~^ ERROR no rules expected
 
     assert!(true "whatever" blah);
-    //~^ WARN unexpected string literal
+    //~^ ERROR unexpected string literal
     //~^^ ERROR no rules expected
 
     assert!(true;);
-    //~^ WARN macro requires an expression
+    //~^ ERROR macro requires an expression
 
     assert!(false || true "error message");
-    //~^ WARN unexpected string literal
+    //~^ ERROR unexpected string literal
 }
diff --git a/src/test/ui/macros/assert-trailing-junk.stderr b/src/test/ui/macros/assert-trailing-junk.stderr
index 4d18a531a800c..84a6768b3f453 100644
--- a/src/test/ui/macros/assert-trailing-junk.stderr
+++ b/src/test/ui/macros/assert-trailing-junk.stderr
@@ -18,15 +18,13 @@ LL |     assert!(true, "whatever" blah);
    |                             |
    |                             help: missing comma here
 
-warning: unexpected string literal
+error: unexpected string literal
   --> $DIR/assert-trailing-junk.rs:15:18
    |
 LL |     assert!(true "whatever" blah);
    |                 -^^^^^^^^^^
    |                 |
    |                 help: try adding a comma
-   |
-   = note: this is going to be an error in the future
 
 error: no rules expected the token `blah`
   --> $DIR/assert-trailing-junk.rs:15:29
@@ -36,25 +34,21 @@ LL |     assert!(true "whatever" blah);
    |                            |
    |                            help: missing comma here
 
-warning: macro requires an expression as an argument
+error: macro requires an expression as an argument
   --> $DIR/assert-trailing-junk.rs:19:5
    |
 LL |     assert!(true;);
    |     ^^^^^^^^^^^^-^^
    |                 |
    |                 help: try removing semicolon
-   |
-   = note: this is going to be an error in the future
 
-warning: unexpected string literal
+error: unexpected string literal
   --> $DIR/assert-trailing-junk.rs:22:27
    |
 LL |     assert!(false || true "error message");
    |                          -^^^^^^^^^^^^^^^
    |                          |
    |                          help: try adding a comma
-   |
-   = note: this is going to be an error in the future
 
-error: aborting due to 4 previous errors
+error: aborting due to 7 previous errors