diff --git a/src/renderer.zig b/src/renderer.zig
index e761c47..63743fe 100644
--- a/src/renderer.zig
+++ b/src/renderer.zig
@@ -53,45 +53,59 @@ pub const Renderer = struct {
     }
 
     pub fn renderString(self: *const Renderer, template: []const u8, writer: anytype) RenderError!void {
+        var arena = std.heap.ArenaAllocator.init(self.allocator);
+        defer arena.deinit();
+        const alloc = arena.allocator();
+
         var p = parser.Parser.init(template);
-        const nodes = try p.parse(self.allocator);
+        const nodes = try p.parse(alloc);
+        defer {
+            for (nodes) |node| node.deinit(alloc);
+            alloc.free(nodes);
+        }
+
         for (nodes) |node| {
-            try self.renderNode(node, writer);
+            try self.renderNode(alloc, node, writer);
         }
     }
 
-    fn renderNode(self: *const Renderer, node: parser.Node, writer: anytype) RenderError!void {
+    fn renderNode(self: *const Renderer, alloc: Allocator, node: parser.Node, writer: anytype) RenderError!void {
         switch (node.type) {
             .text => try writer.writeAll(node.text.?.content),
             .variable => {
                 const var_name = node.variable.?.expr;
                 var value: Value = self.context.get(var_name) orelse Value.null;
-                var buf = ArrayListUnmanaged(u8){};
-                defer buf.deinit(self.allocator);
 
                 var is_safe = false;
 
                 for (node.variable.?.filters) |f| {
-                    const filter_fn = builtin_filters.get(f.name) orelse continue;
-                    value = try filter_fn(self.allocator, value, Value{.string = f.arg orelse ""});
+                    const filter_fn = builtin_filters.get(f.name) orelse return error.UnknownFilter;
+
+                    const arg = if (f.arg) |a| Value{ .string = a } else null;
+                    value = try filter_fn(alloc, value, arg);
+
                     if (std.mem.eql(u8, f.name, "safe")) is_safe = true;
                 }
 
                 if (!is_safe) {
                     if (builtin_filters.get("escape")) |escape_fn| {
-                        value = try escape_fn(self.allocator, value, null);
+                        value = try escape_fn(alloc, value, null);
                     }
                 }
 
-                try self.valueToString(&buf, value);
+                var buf = ArrayListUnmanaged(u8){};
+                defer buf.deinit(alloc);
+
+                try self.valueToString(alloc, &buf, value);
                 try writer.writeAll(buf.items);
             },
             else => unreachable,
         }
     }
 
-    fn valueToString(self: *const Renderer, buf: *ArrayListUnmanaged(u8), value: Value) !void {
-        var w = buf.writer(self.allocator);
+    fn valueToString(self: *const Renderer, alloc: Allocator, buf: *ArrayListUnmanaged(u8), value: Value) !void {
+        _ = self;
+        var w = buf.writer(alloc);
         switch (value) {
             .null => try w.writeAll("null"),
             .bool => |b| try w.print("{}", .{b}),