diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 297120da284..1c6810bdaf9 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -439,6 +439,7 @@ impl clean::GenericBound {
                 let modifier_str = match modifier {
                     hir::TraitBoundModifier::None => "",
                     hir::TraitBoundModifier::Maybe => "?",
+                    hir::TraitBoundModifier::Negative => "!",
                     // ~const is experimental; do not display those bounds in rustdoc
                     hir::TraitBoundModifier::MaybeConst => "",
                 };
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index 62aab46fa7e..b5bebb70593 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -533,6 +533,10 @@ pub(crate) fn from_trait_bound_modifier(
         None => TraitBoundModifier::None,
         Maybe => TraitBoundModifier::Maybe,
         MaybeConst => TraitBoundModifier::MaybeConst,
+        // FIXME(negative-bounds): This bound should be rendered negative, but
+        // since that's experimental, maybe let's not add it to the rustdoc json
+        // API just now...
+        Negative => TraitBoundModifier::None,
     }
 }
 
diff --git a/src/tools/rustfmt/src/types.rs b/src/tools/rustfmt/src/types.rs
index 01e2fb6e61e..9ebe38cc25f 100644
--- a/src/tools/rustfmt/src/types.rs
+++ b/src/tools/rustfmt/src/types.rs
@@ -552,6 +552,8 @@ impl Rewrite for ast::GenericBound {
                     ast::TraitBoundModifier::MaybeConstMaybe => poly_trait_ref
                         .rewrite(context, shape.offset_left(8)?)
                         .map(|s| format!("~const ?{}", s)),
+                    rustc_ast::TraitBoundModifier::Negative
+                    | rustc_ast::TraitBoundModifier::MaybeConstNegative => None,
                 };
                 rewrite.map(|s| if has_paren { format!("({})", s) } else { s })
             }