diff --git a/src/AstGen.zig b/src/AstGen.zig
index 1e21f2a..a137046 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -1139,7 +1139,7 @@ fn assign(gi: *GenIr, scope: *Scope, node: *const Ast.Node) InnerError!void {
         _ = try gi.addBinaryNode(.store, decl.inst_index.toRef(), expr_result);
         return;
     }
-    return fail(astgen, identifier_node, "unknown identifier", .{});
+    _ = try gi.addStrTok(.decl_ref, name_str.index, node.loc.start);
 }
 
 fn assignOp(
@@ -1153,19 +1153,22 @@ fn assignOp(
     const expr_node = node.data.bin.rhs.?;
     const name_str = try astgen.strFromNode(identifier_node);
 
-    if (scope.lookup(name_str.index)) |decl| {
-        const lhs = try gi.addUnaryNode(.load, decl.inst_index.toRef());
-        const rhs = try expr(gi, scope, expr_node);
+    const lhs = if (scope.lookup(name_str.index)) |decl| blk: {
+        const inst_ref = decl.inst_index.toRef();
+        _ = try gi.addUnaryNode(.load, inst_ref);
+        break :blk inst_ref;
+    } else blk: {
+        break :blk try gi.addStrTok(.decl_ref, name_str.index, node.loc.start);
+    };
 
-        const result = switch (op_inst_tag) {
-            .add => try gi.addBinaryNode(.add, lhs, rhs),
-            .sub => try gi.addBinaryNode(.sub, lhs, rhs),
-            else => unreachable,
-        };
-        _ = try gi.addBinaryNode(.store, decl.inst_index.toRef(), result);
-        return;
-    }
-    return fail(astgen, identifier_node, "unknown identifier", .{});
+    const rhs = try expr(gi, scope, expr_node);
+
+    const result = switch (op_inst_tag) {
+        .add => try gi.addBinaryNode(.add, lhs, rhs),
+        .sub => try gi.addBinaryNode(.sub, lhs, rhs),
+        else => unreachable,
+    };
+    _ = try gi.addBinaryNode(.store, lhs, result);
 }
 
 fn choiceStmt(gi: *GenIr, scope: *Scope, node: *const Ast.Node) InnerError!void {