diff --git a/CHANGELOG.md b/CHANGELOG.md
index 30da409643..977198bd4c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -57,6 +57,7 @@
 - Improve negation handling in combination with and/or to simplify generated code (especially coming out of pattern matching). https://github.com/rescript-lang/rescript-compiler/pull/7138
 - optimize JavaScript code generation by using x == null checks and improving type-based optimizations for string/number literals. https://github.com/rescript-lang/rescript-compiler/pull/7141
 - Improve pattern matching on optional fields. https://github.com/rescript-lang/rescript-compiler/pull/7143 https://github.com/rescript-lang/rescript-compiler/pull/7144
+- Optimize compilation of switch statements for untagged variants when there are no literal cases. https://github.com/rescript-lang/rescript-compiler/pull/7135
 
 
 #### :house: Internal
diff --git a/compiler/core/lam_compile.ml b/compiler/core/lam_compile.ml
index b773eff0ed..22b3ffa2b8 100644
--- a/compiler/core/lam_compile.ml
+++ b/compiler/core/lam_compile.ml
@@ -723,7 +723,7 @@ let compile output_prefix =
           (* [e] will be used twice  *)
           let dispatch e =
             let is_a_literal_case =
-              if block_cases <> [] then
+              if untagged then
                 E.is_a_literal_case
                   ~literal_cases:(get_literal_cases sw_names)
                   ~block_cases e
@@ -732,21 +732,41 @@ let compile output_prefix =
                   ~has_null_undefined_other:(has_null_undefined_other sw_names)
                   e
             in
-            S.if_ is_a_literal_case
-              (compile_cases ~cxt ~switch_exp:e ~block_cases
-                 ~default:sw_num_default ~get_tag:get_const_tag sw_consts)
-              ~else_:
-                (compile_cases ~untagged ~cxt
-                   ~switch_exp:(if untagged then e else E.tag ~name:tag_name e)
-                   ~block_cases ~default:sw_blocks_default
-                   ~get_tag:get_block_tag sw_blocks)
+            let eq_default d1 d2 =
+              match (d1, d2) with
+              | Default lam1, Default lam2 -> Lam.eq_approx lam1 lam2
+              | Complete, Complete -> true
+              | NonComplete, NonComplete -> true
+              | _ -> false
+            in
+            if
+              untagged
+              && List.length sw_consts = 0
+              && eq_default sw_num_default sw_blocks_default
+            then
+              compile_cases ~untagged ~cxt
+                ~switch_exp:(if untagged then e else E.tag ~name:tag_name e)
+                ~block_cases ~default:sw_blocks_default ~get_tag:get_block_tag
+                sw_blocks
+            else
+              [
+                S.if_ is_a_literal_case
+                  (compile_cases ~cxt ~switch_exp:e ~block_cases
+                     ~default:sw_num_default ~get_tag:get_const_tag sw_consts)
+                  ~else_:
+                    (compile_cases ~untagged ~cxt
+                       ~switch_exp:
+                         (if untagged then e else E.tag ~name:tag_name e)
+                       ~block_cases ~default:sw_blocks_default
+                       ~get_tag:get_block_tag sw_blocks);
+              ]
           in
           match e.expression_desc with
-          | J.Var _ -> [dispatch e]
+          | J.Var _ -> dispatch e
           | _ ->
             let v = Ext_ident.create_tmp () in
             (* Necessary avoid duplicated computation*)
-            [S.define_variable ~kind:Variable v e; dispatch (E.var v)])
+            S.define_variable ~kind:Variable v e :: dispatch (E.var v))
     in
     match lambda_cxt.continuation with
     (* Needs declare first *)
diff --git a/tests/tests/src/UntaggedVariants.mjs b/tests/tests/src/UntaggedVariants.mjs
index 3dfee9a956..95d20f5767 100644
--- a/tests/tests/src/UntaggedVariants.mjs
+++ b/tests/tests/src/UntaggedVariants.mjs
@@ -376,10 +376,6 @@ let TestFunctionCase = {
 let someJson = '[{"name": "Haan"}, {"name": "Mr"}, false]';
 
 function check$1(s) {
-  if (s === undefined || s === null || s === false || s === true) {
-    console.log("Nope...");
-    return;
-  }
   if (Array.isArray(s)) {
     if (s.length !== 3) {
       console.log("Nope...");
@@ -388,46 +384,40 @@ function check$1(s) {
     let match = s[0];
     if (match === true) {
       let match$1 = s[1];
-      if (match$1 === false) {
-        let match$2 = s[2];
-        if (match$2 === undefined || match$2 === null || match$2 === false || match$2 === true) {
-          console.log("Nope...");
-          return;
-        }
-        if (Array.isArray(match$2)) {
-          if (match$2.length !== 2) {
-            console.log("Nope...");
-            return;
-          }
-          let match$3 = match$2[0];
-          if (match$3 === undefined || match$3 === null || match$3 === false || match$3 === true) {
-            console.log("Nope...");
-            return;
-          }
-          if (match$3 === "My name is") {
-            let match$4 = match$2[1];
-            if (match$4 === undefined || match$4 === null || match$4 === false || match$4 === true) {
+      if (match$1 === undefined || match$1 === null || match$1 === false || match$1 === true) {
+        if (match$1 === false) {
+          let match$2 = s[2];
+          if (Array.isArray(match$2)) {
+            if (match$2.length !== 2) {
               console.log("Nope...");
               return;
             }
-            if (typeof match$4 === "number") {
-              if (match$4 !== 10) {
+            let match$3 = match$2[0];
+            if (typeof match$3 === "string") {
+              if (match$3 === "My name is") {
+                let match$4 = match$2[1];
+                if (typeof match$4 === "number") {
+                  if (match$4 !== 10) {
+                    console.log("Nope...");
+                  } else {
+                    console.log("yup");
+                  }
+                  return;
+                }
                 console.log("Nope...");
-              } else {
-                console.log("yup");
+                return;
               }
+              console.log("Nope...");
               return;
             }
             console.log("Nope...");
             return;
-          } else {
-            console.log("Nope...");
-            return;
           }
-        } else {
           console.log("Nope...");
           return;
         }
+        console.log("Nope...");
+        return;
       } else {
         console.log("Nope...");
         return;
diff --git a/tests/tests/src/and_or_simplify.mjs b/tests/tests/src/and_or_simplify.mjs
index 968359e1b8..dd7011f8b0 100644
--- a/tests/tests/src/and_or_simplify.mjs
+++ b/tests/tests/src/and_or_simplify.mjs
@@ -6,10 +6,10 @@ function check_null_eq_typeof(x) {
 }
 
 function check_null_neq_typeof(x) {
-  if (typeof x !== "boolean") {
-    return 4;
-  } else {
+  if (typeof x === "boolean") {
     return 3;
+  } else {
+    return 4;
   }
 }
 
@@ -18,10 +18,10 @@ function check_undefined_eq_typeof(x) {
 }
 
 function check_undefined_neq_typeof(x) {
-  if (typeof x !== "boolean") {
-    return 4;
-  } else {
+  if (typeof x === "boolean") {
     return 3;
+  } else {
+    return 4;
   }
 }
 
diff --git a/tests/tests/src/core/Core_JsonTests.mjs b/tests/tests/src/core/Core_JsonTests.mjs
index 1f4ff3bfc5..a830175589 100644
--- a/tests/tests/src/core/Core_JsonTests.mjs
+++ b/tests/tests/src/core/Core_JsonTests.mjs
@@ -5,19 +5,17 @@ import * as Test from "./Test.mjs";
 function decodeJsonTest() {
   let json = {"someProp":{"otherProp": null, "thirdProp": [true, false]}};
   let decodedCorrectly;
-  if (json === null || !(typeof json === "object" && !Array.isArray(json))) {
-    decodedCorrectly = false;
-  } else {
+  if (typeof json === "object" && !Array.isArray(json)) {
     let match = json["someProp"];
-    if (match !== undefined && !(match === null || !(typeof match === "object" && !Array.isArray(match)))) {
+    if (match !== undefined && typeof match === "object" && !Array.isArray(match)) {
       let match$1 = match["thirdProp"];
-      if (match$1 !== undefined && !(match$1 === null || !(Array.isArray(match$1) && match$1.length === 2))) {
+      if (match$1 !== undefined && Array.isArray(match$1) && match$1.length === 2) {
         let match$2 = match$1[0];
-        if (match$2 === null || !(typeof match$2 === "boolean" && match$2)) {
-          decodedCorrectly = false;
-        } else {
+        if (typeof match$2 === "boolean" && match$2) {
           let match$3 = match$1[1];
-          decodedCorrectly = match$3 === null ? false : typeof match$3 === "boolean" && !match$3;
+          decodedCorrectly = typeof match$3 === "boolean" && !match$3;
+        } else {
+          decodedCorrectly = false;
         }
       } else {
         decodedCorrectly = false;
@@ -25,6 +23,8 @@ function decodeJsonTest() {
     } else {
       decodedCorrectly = false;
     }
+  } else {
+    decodedCorrectly = false;
   }
   Test.run([
     [
diff --git a/tests/tests/src/json_decorders.mjs b/tests/tests/src/json_decorders.mjs
new file mode 100644
index 0000000000..cac0277cc7
--- /dev/null
+++ b/tests/tests/src/json_decorders.mjs
@@ -0,0 +1,59 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+import * as $$Array from "rescript/lib/es6/Array.js";
+
+function decodeUser(json) {
+  if (!(typeof json === "object" && !Array.isArray(json))) {
+    return;
+  }
+  let id = json.id;
+  if (typeof id !== "string") {
+    return;
+  }
+  let name = json.name;
+  if (typeof name !== "string") {
+    return;
+  }
+  let age = json.age;
+  if (typeof age !== "number") {
+    return;
+  }
+  let email = json.email;
+  let tmp;
+  tmp = typeof email === "string" ? email : undefined;
+  return {
+    id: id,
+    name: name,
+    age: age | 0,
+    email: tmp
+  };
+}
+
+function decodeGroup(json) {
+  if (!(typeof json === "object" && !Array.isArray(json))) {
+    return;
+  }
+  let id = json.id;
+  if (typeof id !== "string") {
+    return;
+  }
+  let name = json.name;
+  if (typeof name !== "string") {
+    return;
+  }
+  let users = json.users;
+  if (Array.isArray(users)) {
+    return {
+      id: id,
+      name: name,
+      users: $$Array.filterMap(users, decodeUser)
+    };
+  }
+  
+}
+
+export {
+  decodeUser,
+  decodeGroup,
+}
+/* No side effect */
diff --git a/tests/tests/src/json_decorders.res b/tests/tests/src/json_decorders.res
new file mode 100644
index 0000000000..3f792eaaf0
--- /dev/null
+++ b/tests/tests/src/json_decorders.res
@@ -0,0 +1,45 @@
+type user = {
+  id: string,
+  name: string,
+  age: int,
+  email: option<string>,
+}
+
+type group = {
+  id: string,
+  name: string,
+  users: array<user>,
+}
+
+let decodeUser = json => {
+  switch json {
+  | JSON.Object(dict{
+      "id": JSON.String(id),
+      "name": String(name),
+      "age": Number(age),
+      "email": ?email,
+    }) =>
+    Some({
+      id,
+      name,
+      age: age->Float.toInt,
+      email: switch email {
+      | Some(String(email)) => Some(email)
+      | _ => None
+      },
+    })
+  | _ => None
+  }
+}
+
+let decodeGroup = json => {
+  switch json {
+  | JSON.Object(dict{"id": JSON.String(id), "name": String(name), "users": Array(users)}) =>
+    Some({
+      id,
+      name,
+      users: users->Array.filterMap(decodeUser),
+    })
+  | _ => None
+  }
+}
diff --git a/tests/tests/src/pattern_match_json.mjs b/tests/tests/src/pattern_match_json.mjs
index 378f82afeb..37b7157300 100644
--- a/tests/tests/src/pattern_match_json.mjs
+++ b/tests/tests/src/pattern_match_json.mjs
@@ -4,12 +4,6 @@ import * as Primitive_option from "rescript/lib/es6/Primitive_option.js";
 
 function decodeGroup(group) {
   let id = group.id;
-  if (id == null) {
-    return [
-      "e",
-      "f"
-    ];
-  }
   if (typeof id !== "string") {
     return [
       "e",
@@ -17,15 +11,15 @@ function decodeGroup(group) {
     ];
   }
   let name = group.name;
-  if (typeof name !== "string") {
+  if (typeof name === "string") {
     return [
-      "e",
-      "f"
+      id,
+      name
     ];
   } else {
     return [
-      id,
-      name
+      "e",
+      "f"
     ];
   }
 }