diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index b2e5c8834b8ff..9c4d3becbdaef 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -154,7 +154,7 @@ impl From<clean::ItemKind> for ItemEnum {
             }
             ImportItem(i) => ItemEnum::ImportItem(i.into()),
             StructItem(s) => ItemEnum::StructItem(s.into()),
-            UnionItem(u) => ItemEnum::StructItem(u.into()),
+            UnionItem(u) => ItemEnum::UnionItem(u.into()),
             StructFieldItem(f) => ItemEnum::StructFieldItem(f.into()),
             EnumItem(e) => ItemEnum::EnumItem(e.into()),
             VariantItem(v) => ItemEnum::VariantItem(v.into()),
@@ -205,11 +205,10 @@ impl From<clean::Struct> for Struct {
     }
 }
 
-impl From<clean::Union> for Struct {
+impl From<clean::Union> for Union {
     fn from(struct_: clean::Union) -> Self {
         let clean::Union { generics, fields, fields_stripped } = struct_;
-        Struct {
-            struct_type: StructType::Union,
+        Union {
             generics: generics.into(),
             fields_stripped,
             fields: ids(fields),
diff --git a/src/librustdoc/json/mod.rs b/src/librustdoc/json/mod.rs
index a7c875fb7480b..876b1b56dee6d 100644
--- a/src/librustdoc/json/mod.rs
+++ b/src/librustdoc/json/mod.rs
@@ -243,7 +243,7 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
                     )
                 })
                 .collect(),
-            format_version: 2,
+            format_version: 3,
         };
         let mut p = self.out_path.clone();
         p.push(output.index.get(&output.root).unwrap().name.clone().unwrap());
diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
index 3fb2a32d5a0a3..083f99e4a681a 100644
--- a/src/rustdoc-json-types/lib.rs
+++ b/src/rustdoc-json-types/lib.rs
@@ -194,6 +194,7 @@ pub enum ItemEnum {
     },
     ImportItem(Import),
 
+    UnionItem(Union),
     StructItem(Struct),
     StructFieldItem(Type),
     EnumItem(Enum),
@@ -238,6 +239,14 @@ pub struct Module {
     pub items: Vec<Id>,
 }
 
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct Union {
+    pub generics: Generics,
+    pub fields_stripped: bool,
+    pub fields: Vec<Id>,
+    pub impls: Vec<Id>,
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 pub struct Struct {
     pub struct_type: StructType,
@@ -270,7 +279,6 @@ pub enum StructType {
     Plain,
     Tuple,
     Unit,
-    Union,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
diff --git a/src/test/rustdoc-json/unions/union.rs b/src/test/rustdoc-json/unions/union.rs
new file mode 100644
index 0000000000000..ac2eb797791f3
--- /dev/null
+++ b/src/test/rustdoc-json/unions/union.rs
@@ -0,0 +1,7 @@
+// @has union.json "$.index[*][?(@.name=='Union')].visibility" \"public\"
+// @has - "$.index[*][?(@.name=='Union')].kind" \"union\"
+// @!has - "$.index[*][?(@.name=='Union')].inner.struct_type"
+pub union Union {
+    int: i32,
+    float: f32,
+}