diff --git a/compiler/forget/src/HIR/BuildHIR.ts b/compiler/forget/src/HIR/BuildHIR.ts
index 969998d275..c8b1ae8f51 100644
--- a/compiler/forget/src/HIR/BuildHIR.ts
+++ b/compiler/forget/src/HIR/BuildHIR.ts
@@ -1790,7 +1790,36 @@ function lowerAssignment(
   switch (lvalueNode.type) {
     case "Identifier": {
       const lvalue = lvaluePath as NodePath<t.Identifier>;
-      const place = lowerIdentifier(builder, lvalue);
+      const identifier = builder.resolveIdentifier(lvalue);
+      if (identifier == null) {
+        if (kind === InstructionKind.Reassign) {
+          // Trying to reassign a global is not allowed
+          builder.errors.push({
+            reason: `(BuildHIR::lowerAssignment) Assigning to an identifier defined outside the function scope is not supported.`,
+            severity: ErrorSeverity.InvalidInput,
+            nodePath: lvalue,
+          });
+        } else {
+          // Else its an internal error bc we couldn't find the binding
+          builder.errors.push({
+            reason: `(BuildHIR::lowerAssignment) Could not find binding for declaration.`,
+            severity: ErrorSeverity.Invariant,
+            nodePath: lvalue,
+          });
+        }
+        return {
+          kind: "UnsupportedNode",
+          loc: lvalue.node.loc ?? GeneratedSource,
+          node: lvalue.node,
+        };
+      }
+
+      const place: Place = {
+        kind: "Identifier",
+        identifier: identifier,
+        effect: Effect.Unknown,
+        loc: lvalue.node.loc ?? GeneratedSource,
+      };
       builder.push({
         id: makeInstructionId(0),
         lvalue: { place: { ...place }, kind },
diff --git a/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.expect.md b/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.expect.md
index b92f21f70a..fed25d84e4 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.expect.md
+++ b/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.expect.md
@@ -68,6 +68,9 @@ function foo([a, b], { c, d, e = "e" }, f = "f", ...args) {
     default: {
     }
   }
+
+  // Cannot assign to globals
+  someUnknownGlobal = true;
 }
 
 ```
@@ -400,6 +403,14 @@ function foo([a, b], { c, d, e = "e" }, f = "f", ...args) {
   59 |     }
   60 |     case foo(): {
   61 |     }
+
+[ReactForget] InvalidInputError: (BuildHIR::lowerAssignment) Assigning to an identifier defined outside the function scope is not supported.
+  67 |
+  68 |   // Cannot assign to globals
+> 69 |   someUnknownGlobal = true;
+     |   ^^^^^^^^^^^^^^^^^
+  70 | }
+  71 |
 ```
           
       
\ No newline at end of file
diff --git a/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.js b/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.js
index fd71c0cb2d..54696dc410 100644
--- a/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.js
+++ b/compiler/forget/src/__tests__/fixtures/hir/error.todo-kitchensink.js
@@ -64,4 +64,7 @@ function foo([a, b], { c, d, e = "e" }, f = "f", ...args) {
     default: {
     }
   }
+
+  // Cannot assign to globals
+  someUnknownGlobal = true;
 }