diff --git a/compiler/core/lam_compile.ml b/compiler/core/lam_compile.ml
index 680bce50a7..5de8127194 100644
--- a/compiler/core/lam_compile.ml
+++ b/compiler/core/lam_compile.ml
@@ -814,9 +814,23 @@ let compile output_prefix =
       | _ -> false
     in
     let clause_is_not_typeof (tag, _) = tag_is_not_typeof tag in
-    let clause_is_object_typeof = function
-      | Ast_untagged_variants.Untagged ObjectType, _ -> true
-      | _ -> false
+    let has_null_clause clauses =
+      Ext_list.exists clauses (fun (tag, _) ->
+          match (tag : Ast_untagged_variants.tag_type) with
+          | Null -> true
+          | _ -> false)
+    in
+    let has_object_clause clauses =
+      Ext_list.exists clauses (fun (tag, _) ->
+          match (tag : Ast_untagged_variants.tag_type) with
+          | Untagged ObjectType -> true
+          | _ -> false)
+    in
+    let has_array_clause clauses =
+      Ext_list.exists clauses (fun (tag, _) ->
+          match (tag : Ast_untagged_variants.tag_type) with
+          | Untagged (InstanceType Array) -> true
+          | _ -> false)
     in
     let switch ?default ?declaration e clauses =
       let not_typeof_clauses, typeof_clauses =
@@ -831,17 +845,42 @@ let compile output_prefix =
             (E.emit_check (IsInstanceOf (instance_type, Expr e)))
             switch_body
             ~else_:[build_if_chain rest]
-        | _ ->
-          let typeof_switch () =
+        | _ -> (
+          let switch_stmt =
             S.string_switch ?default ?declaration (E.typeof e) typeof_clauses
           in
-          if has_null_case && List.exists clause_is_object_typeof typeof_clauses
-          then
-            match default with
-            | Some default_body ->
-              S.if_ (E.is_null e) default_body ~else_:[typeof_switch ()]
-            | None -> typeof_switch ()
-          else typeof_switch ()
+          (* If there's an Object clause but no Null clause and null is a possible value,
+             we need to exclude null from matching the Object case.
+             In JavaScript, typeof null === "object", so null would incorrectly match Object. *)
+          let needs_null_check =
+            has_null_case
+            && (not (has_null_clause typeof_clauses))
+            && has_object_clause typeof_clauses
+          in
+          (* If Array is a possible block type but there's no Array clause and there is an Object clause,
+             we need to exclude arrays from matching the Object case.
+             In JavaScript, typeof [] === "object", so arrays would incorrectly match Object. *)
+          let needs_array_check =
+            List.mem Ast_untagged_variants.(InstanceType Array) block_cases
+            && (not (has_array_clause typeof_clauses))
+            && has_object_clause typeof_clauses
+          in
+          let cond =
+            match (needs_null_check, needs_array_check) with
+            | true, true ->
+              Some (E.and_ (E.not (E.is_null e)) (E.not (E.is_array e)))
+            | true, false -> Some (E.not (E.is_null e))
+            | false, true -> Some (E.not (E.is_array e))
+            | false, false -> None
+          in
+          match cond with
+          | Some c ->
+            S.if_ c [switch_stmt]
+              ~else_:
+                (match default with
+                | Some block -> block
+                | None -> [])
+          | None -> switch_stmt)
       in
       build_if_chain not_typeof_clauses
     in
diff --git a/tests/tests/src/JSONSwitchNullCheck_test.mjs b/tests/tests/src/JSONSwitchNullCheck_test.mjs
new file mode 100644
index 0000000000..d1152f8bce
--- /dev/null
+++ b/tests/tests/src/JSONSwitchNullCheck_test.mjs
@@ -0,0 +1,199 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+
+import * as Mocha from "mocha";
+import * as Test_utils from "./test_utils.mjs";
+
+let jsonNull = null;
+
+let jsonArray = ["a", "b"];
+
+let jsonObject = {"key": "value"};
+
+let jsonString = "hello";
+
+let jsonNumber = 42;
+
+let jsonBool = true;
+
+Mocha.describe("JSONSwitchNullCheck_test", () => {
+  Mocha.describe("JSON direct switch with Null - should NOT match Object", () => {
+    Mocha.test("switch null { | Object(_) => Object | Array(_) => Array | _ => default }", () => {
+      let result;
+      if (Array.isArray(jsonNull)) {
+        result = "Array";
+      } else if (jsonNull !== null && !Array.isArray(jsonNull)) {
+        switch (typeof jsonNull) {
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 26, characters 11-18", result, "default");
+    });
+    Mocha.test("switch null { | Object(_) => Object | String(_) => String | _ => default }", () => {
+      let result;
+      if (jsonNull !== null && !Array.isArray(jsonNull)) {
+        switch (typeof jsonNull) {
+          case "string" :
+            result = "String";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 39, characters 11-18", result, "default");
+    });
+    Mocha.test("switch null { | Object(_) => Object | Number(_) => Number | _ => default }", () => {
+      let result;
+      if (jsonNull !== null && !Array.isArray(jsonNull)) {
+        switch (typeof jsonNull) {
+          case "number" :
+            result = "Number";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 52, characters 11-18", result, "default");
+    });
+    Mocha.test("switch null { | Object(_) => Object | Array(_) => Array | String(_) => String | _ => default }", () => {
+      let result;
+      if (Array.isArray(jsonNull)) {
+        result = "Array";
+      } else if (jsonNull !== null && !Array.isArray(jsonNull)) {
+        switch (typeof jsonNull) {
+          case "string" :
+            result = "String";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 66, characters 11-18", result, "default");
+    });
+  });
+  Mocha.describe("JSON direct switch with Array - should NOT match Object", () => {
+    Mocha.test("switch array { | Object(_) => Object | String(_) => String | _ => default }", () => {
+      let result;
+      if (jsonArray !== null && !Array.isArray(jsonArray)) {
+        switch (typeof jsonArray) {
+          case "string" :
+            result = "String";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 81, characters 11-18", result, "default");
+    });
+    Mocha.test("switch array { | Object(_) => Object | Number(_) => Number | _ => default }", () => {
+      let result;
+      if (jsonArray !== null && !Array.isArray(jsonArray)) {
+        switch (typeof jsonArray) {
+          case "number" :
+            result = "Number";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 94, characters 11-18", result, "default");
+    });
+    Mocha.test("switch array { | Object(_) => Object | Boolean(_) => Boolean | _ => default }", () => {
+      let result;
+      if (jsonArray !== null && !Array.isArray(jsonArray)) {
+        switch (typeof jsonArray) {
+          case "boolean" :
+            result = "Boolean";
+            break;
+          case "object" :
+            result = "Object";
+            break;
+          default:
+            result = "default";
+        }
+      } else {
+        result = "default";
+      }
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 107, characters 11-18", result, "default");
+    });
+  });
+  Mocha.describe("JSON switch - correct positive cases", () => {
+    Mocha.test("switch object { | Object(_) => Object | _ => default }", () => {
+      let result;
+      result = typeof jsonObject === "object" && jsonObject !== null && !Array.isArray(jsonObject) ? "Object" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 120, characters 11-18", result, "Object");
+    });
+    Mocha.test("switch array { | Array(_) => Array | _ => default }", () => {
+      let result;
+      result = Array.isArray(jsonArray) ? "Array" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 131, characters 11-18", result, "Array");
+    });
+    Mocha.test("switch string { | String(_) => String | _ => default }", () => {
+      let result;
+      result = typeof jsonString === "string" ? "String" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 142, characters 11-18", result, "String");
+    });
+    Mocha.test("switch number { | Number(_) => Number | _ => default }", () => {
+      let result;
+      result = typeof jsonNumber === "number" ? "Number" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 153, characters 11-18", result, "Number");
+    });
+    Mocha.test("switch bool { | Boolean(_) => Boolean | _ => default }", () => {
+      let result;
+      result = typeof jsonBool === "boolean" ? "Boolean" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 164, characters 11-18", result, "Boolean");
+    });
+    Mocha.test("switch null { | Null => Null | _ => default }", () => {
+      let result;
+      result = jsonNull === null ? "Null" : "default";
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 175, characters 11-18", result, "Null");
+    });
+    Mocha.test("switch null { | Null => Null | Object(_) => Object | _ => default }", () => {
+      let result;
+      result = jsonNull === null ? "Null" : (
+          typeof jsonNull === "object" && !Array.isArray(jsonNull) ? "Object" : "default"
+        );
+      Test_utils.eq("File \"JSONSwitchNullCheck_test.res\", line 187, characters 11-18", result, "Null");
+    });
+  });
+});
+
+export {
+  jsonNull,
+  jsonArray,
+  jsonObject,
+  jsonString,
+  jsonNumber,
+  jsonBool,
+}
+/*  Not a pure module */
diff --git a/tests/tests/src/JSONSwitchNullCheck_test.res b/tests/tests/src/JSONSwitchNullCheck_test.res
new file mode 100644
index 0000000000..612492fc67
--- /dev/null
+++ b/tests/tests/src/JSONSwitchNullCheck_test.res
@@ -0,0 +1,191 @@
+open Mocha
+open Test_utils
+
+// Test cases for JSON switch with null and various block types
+// These test the fix for: null incorrectly matching Object case in switch
+
+// Helper to create test JSON values
+let jsonNull: JSON.t = %raw(`null`)
+let jsonArray: JSON.t = %raw(`["a", "b"]`)
+let jsonObject: JSON.t = %raw(`{"key": "value"}`)
+let jsonString: JSON.t = %raw(`"hello"`)
+let jsonNumber: JSON.t = %raw(`42`)
+let jsonBool: JSON.t = %raw(`true`)
+
+describe(__MODULE__, () => {
+  describe("JSON direct switch with Null - should NOT match Object", () => {
+    // Test: Object | Array | _ with null - null should go to default
+    test(
+      "switch null { | Object(_) => Object | Array(_) => Array | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Object(_) => "Object"
+        | Array(_) => "Array"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+
+    // Test: Object | String | _ with null - null should go to default
+    test(
+      "switch null { | Object(_) => Object | String(_) => String | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Object(_) => "Object"
+        | String(_) => "String"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+
+    // Test: Object | Number | _ with null - null should go to default
+    test(
+      "switch null { | Object(_) => Object | Number(_) => Number | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Object(_) => "Object"
+        | Number(_) => "Number"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+
+    // Test: Multiple block cases with null - null should go to default
+    test(
+      "switch null { | Object(_) => Object | Array(_) => Array | String(_) => String | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Object(_) => "Object"
+        | Array(_) => "Array"
+        | String(_) => "String"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+  })
+
+  describe("JSON direct switch with Array - should NOT match Object", () => {
+    // Test: Array being matched as Object - Object | String | _ with array
+    test(
+      "switch array { | Object(_) => Object | String(_) => String | _ => default }",
+      () => {
+        let result = switch jsonArray {
+        | Object(_) => "Object"
+        | String(_) => "String"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+
+    // Test: Array being matched as Object - Object | Number | _ with array
+    test(
+      "switch array { | Object(_) => Object | Number(_) => Number | _ => default }",
+      () => {
+        let result = switch jsonArray {
+        | Object(_) => "Object"
+        | Number(_) => "Number"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+
+    // Test: Array being matched as Object - Object | Boolean | _ with array
+    test(
+      "switch array { | Object(_) => Object | Boolean(_) => Boolean | _ => default }",
+      () => {
+        let result = switch jsonArray {
+        | Object(_) => "Object"
+        | Boolean(_) => "Boolean"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "default")
+      },
+    )
+  })
+
+  describe("JSON switch - correct positive cases", () => {
+    test(
+      "switch object { | Object(_) => Object | _ => default }",
+      () => {
+        let result = switch jsonObject {
+        | Object(_) => "Object"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Object")
+      },
+    )
+
+    test(
+      "switch array { | Array(_) => Array | _ => default }",
+      () => {
+        let result = switch jsonArray {
+        | Array(_) => "Array"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Array")
+      },
+    )
+
+    test(
+      "switch string { | String(_) => String | _ => default }",
+      () => {
+        let result = switch jsonString {
+        | String(_) => "String"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "String")
+      },
+    )
+
+    test(
+      "switch number { | Number(_) => Number | _ => default }",
+      () => {
+        let result = switch jsonNumber {
+        | Number(_) => "Number"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Number")
+      },
+    )
+
+    test(
+      "switch bool { | Boolean(_) => Boolean | _ => default }",
+      () => {
+        let result = switch jsonBool {
+        | Boolean(_) => "Boolean"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Boolean")
+      },
+    )
+
+    test(
+      "switch null { | Null => Null | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Null => "Null"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Null")
+      },
+    )
+
+    test(
+      "switch null { | Null => Null | Object(_) => Object | _ => default }",
+      () => {
+        let result = switch jsonNull {
+        | Null => "Null"
+        | Object(_) => "Object"
+        | _ => "default"
+        }
+        eq(__LOC__, result, "Null")
+      },
+    )
+  })
+})
diff --git a/tests/tests/src/UntaggedVariants.mjs b/tests/tests/src/UntaggedVariants.mjs
index b57405ea26..5c1dc4383f 100644
--- a/tests/tests/src/UntaggedVariants.mjs
+++ b/tests/tests/src/UntaggedVariants.mjs
@@ -157,13 +157,15 @@ function classify$5(x) {
   if (Array.isArray(x)) {
     return "array";
   }
-  switch (typeof x) {
-    case "string" :
-      return "string";
-    case "number" :
-      return "int";
-    case "object" :
-      return "Object" + x.name;
+  if (!Array.isArray(x)) {
+    switch (typeof x) {
+      case "string" :
+        return "string";
+      case "number" :
+        return "int";
+      case "object" :
+        return "Object" + x.name;
+    }
   }
 }
 
@@ -188,22 +190,24 @@ function classify$6(x) {
         _0: x
       };
     }
-    switch (typeof x) {
-      case "string" :
-        return {
-          TAG: "JSONString",
-          _0: x
-        };
-      case "number" :
-        return {
-          TAG: "JSONNumber",
-          _0: x
-        };
-      case "object" :
-        return {
-          TAG: "JSONObject",
-          _0: x
-        };
+    if (!Array.isArray(x)) {
+      switch (typeof x) {
+        case "string" :
+          return {
+            TAG: "JSONString",
+            _0: x
+          };
+        case "number" :
+          return {
+            TAG: "JSONNumber",
+            _0: x
+          };
+        case "object" :
+          return {
+            TAG: "JSONObject",
+            _0: x
+          };
+      }
     }
   }
 }
@@ -357,11 +361,13 @@ function classify$9(v) {
   if (Array.isArray(v)) {
     return v[0];
   }
-  switch (typeof v) {
-    case "object" :
-      return v.x;
-    case "function" :
-      return v(3);
+  if (!Array.isArray(v)) {
+    switch (typeof v) {
+      case "object" :
+        return v.x;
+      case "function" :
+        return v(3);
+    }
   }
 }
 
@@ -481,13 +487,15 @@ async function classify$10(a) {
       console.log(await a);
       return;
     }
-    switch (typeof a) {
-      case "string" :
-        console.log(a);
-        return;
-      case "object" :
-        console.log(a.userName);
-        return;
+    if (!Array.isArray(a)) {
+      switch (typeof a) {
+        case "string" :
+          console.log(a);
+          return;
+        case "object" :
+          console.log(a.userName);
+          return;
+      }
     }
   }
 }
@@ -589,13 +597,15 @@ async function classifyAll(t) {
     console.log("WeakMap");
     return;
   }
-  switch (typeof t) {
-    case "string" :
-      console.log(t);
-      return;
-    case "object" :
-      console.log(t.userName);
-      return;
+  if (!Array.isArray(t)) {
+    switch (typeof t) {
+      case "string" :
+        console.log(t);
+        return;
+      case "object" :
+        console.log(t.userName);
+        return;
+    }
   }
 }
 
@@ -629,11 +639,13 @@ function should_not_merge(x) {
   if (x instanceof Date) {
     return "do not merge";
   }
-  switch (typeof x) {
-    case "boolean" :
-      return "boolean";
-    case "object" :
-      return "do not merge";
+  if (!Array.isArray(x)) {
+    switch (typeof x) {
+      case "boolean" :
+        return "boolean";
+      case "object" :
+        return "do not merge";
+    }
   }
 }
 
@@ -644,10 +656,12 @@ function can_merge(x) {
   if (x instanceof Date) {
     return "do not merge";
   }
-  switch (typeof x) {
-    case "boolean" :
-    case "object" :
-      return "merge";
+  if (!Array.isArray(x)) {
+    switch (typeof x) {
+      case "boolean" :
+      case "object" :
+        return "merge";
+    }
   }
 }