diff --git a/src/libsyntax/ext/tt/quoted.rs b/src/libsyntax/ext/tt/quoted.rs
index 13764ebfca1e..670d3614604b 100644
--- a/src/libsyntax/ext/tt/quoted.rs
+++ b/src/libsyntax/ext/tt/quoted.rs
@@ -432,6 +432,6 @@ where
     };
 
     sess.span_diagnostic
-        .span_err(span, "expected one of: `*`,  `+`, or `?`");
+        .span_err(span, "expected one of: `*`, `+`, or `?`");
     (None, KleeneOp::ZeroOrMore)
 }
diff --git a/src/test/compile-fail/issue-39388.rs b/src/test/compile-fail/issue-39388.rs
index 15eef429eab9..3fbbab62d24c 100644
--- a/src/test/compile-fail/issue-39388.rs
+++ b/src/test/compile-fail/issue-39388.rs
@@ -11,7 +11,7 @@
 #![allow(unused_macros)]
 
 macro_rules! assign {
-    (($($a:tt)*) = ($($b:tt))*) => { //~ ERROR expected `*` or `+`
+    (($($a:tt)*) = ($($b:tt))*) => { //~ ERROR 14:22: 14:29: expected one of: `*`, `+`, or `?`
         $($a)* = $($b)*
     }
 }
diff --git a/src/test/compile-fail/macro-at-most-once-rep-ambig.rs b/src/test/compile-fail/macro-at-most-once-rep-ambig.rs
index b0a6ec145e16..89ca30840a98 100644
--- a/src/test/compile-fail/macro-at-most-once-rep-ambig.rs
+++ b/src/test/compile-fail/macro-at-most-once-rep-ambig.rs
@@ -12,6 +12,10 @@ macro_rules! foo {
     ($(a)?) => {}
 }
 
+macro_rules! baz {
+    ($(a),?) => {} // comma separator is meaningless for `?`
+}
+
 macro_rules! bar {
     ($(a)?+) => {}
 }
@@ -20,7 +24,13 @@ pub fn main() {
     foo!(a?a?a); //~ ERROR no rules expected the token `?`
     foo!(a?a); //~ ERROR no rules expected the token `?`
     foo!(a?); //~ ERROR no rules expected the token `?`
-    bar!(); //~ ERROR no rules expected the token `)`
+    baz!(a?a?a); //~ ERROR no rules expected the token `?`
+    baz!(a?a); //~ ERROR no rules expected the token `?`
+    baz!(a?); //~ ERROR no rules expected the token `?`
+    baz!(a,); //~ ERROR no rules expected the token `,`
+    baz!(a?a?a,); //~ ERROR no rules expected the token `?`
+    baz!(a?a,); //~ ERROR no rules expected the token `?`
+    baz!(a?,); //~ ERROR no rules expected the token `?`
+    bar!(); //~ ERROR unexpected end of macro invocation
     bar!(a?); //~ ERROR no rules expected the token `?`
 }
-
diff --git a/src/test/run-pass/macro-at-most-once-rep.rs b/src/test/run-pass/macro-at-most-once-rep.rs
index fa1f90bf6ef9..823f42c45442 100644
--- a/src/test/run-pass/macro-at-most-once-rep.rs
+++ b/src/test/run-pass/macro-at-most-once-rep.rs
@@ -12,6 +12,10 @@ macro_rules! foo {
     ($(a)?) => {}
 }
 
+macro_rules! baz {
+    ($(a),?) => {} // comma separator is meaningless for `?`
+}
+
 macro_rules! bar {
     ($(a)?+) => {}
 }
@@ -19,6 +23,8 @@ macro_rules! bar {
 pub fn main() {
     foo!();
     foo!(a);
+    baz!();
+    baz!(a);
     bar!(a);
     bar!(a?a);
     bar!(a?a?a);