diff --git a/src/http/query.zig b/src/http/query.zig
index 35438f5..1396696 100644
--- a/src/http/query.zig
+++ b/src/http/query.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
+const util = @import("util");
 
-const QueryIter = @import("util").QueryIter;
+const QueryIter = util.QueryIter;
 
 /// Parses a set of query parameters described by the struct `T`.
 ///
@@ -84,6 +85,10 @@ pub fn parseQuery(alloc: std.mem.Allocator, comptime T: type, query: []const u8)
     return (try parse(alloc, T, "", "", fields)) orelse error.NoQuery;
 }
 
+pub fn parseQueryFree(alloc: std.mem.Allocator, val: anytype) void {
+    util.deepFree(alloc, val);
+}
+
 fn decodeString(alloc: std.mem.Allocator, val: []const u8) ![]u8 {
     var list = try std.ArrayList(u8).initCapacity(alloc, val.len);
     errdefer list.deinit();
@@ -142,6 +147,9 @@ fn parse(
         .Struct => |info| {
             var result: T = undefined;
             var fields_specified: usize = 0;
+            errdefer inline for (info.fields) |field, i| {
+                if (fields_specified < i) util.deepFree(alloc, @field(result, field.name));
+            };
 
             inline for (info.fields) |field| {
                 const F = field.field_type;
@@ -151,7 +159,7 @@ fn parse(
                     maybe_value = v;
                 } else if (field.default_value) |default| {
                     if (comptime @sizeOf(F) != 0) {
-                        maybe_value = @ptrCast(*const F, @alignCast(@alignOf(F), default)).*;
+                        maybe_value = try util.deepClone(alloc, @ptrCast(*const F, @alignCast(@alignOf(F), default)).*);
                     } else {
                         maybe_value = std.mem.zeroes(F);
                     }
@@ -227,10 +235,38 @@ fn Intermediary(comptime T: type) type {
     } });
 }
 
-fn parseQueryValue(alloc: std.mem.Allocator, comptime T: type, value: ?[]const u8) !T {
+fn parseQueryValue(alloc: std.mem.Allocator, comptime T: type, maybe_value: ?[]const u8) !T {
     const is_optional = comptime std.meta.trait.is(.Optional)(T);
-    // If param is present, but without an associated value
-    if (value == null) {
+    if (maybe_value) |value| {
+        const Eff = if (is_optional) std.meta.Child(T) else T;
+
+        if (value.len == 0 and is_optional) return null;
+
+        const decoded = try decodeString(alloc, value);
+        errdefer alloc.free(decoded);
+
+        if (comptime std.meta.trait.isZigString(Eff)) return decoded;
+
+        defer alloc.free(decoded);
+
+        const result = if (comptime std.meta.trait.isIntegral(Eff))
+            try std.fmt.parseInt(Eff, decoded, 0)
+        else if (comptime std.meta.trait.isFloat(Eff))
+            try std.fmt.parseFloat(Eff, decoded)
+        else if (comptime std.meta.trait.is(.Enum)(Eff)) blk: {
+            _ = std.ascii.lowerString(decoded, decoded);
+            break :blk std.meta.stringToEnum(Eff, decoded) orelse return error.InvalidEnumValue;
+        } else if (Eff == bool) blk: {
+            _ = std.ascii.lowerString(decoded, decoded);
+            break :blk bool_map.get(decoded) orelse return error.InvalidBool;
+        } else if (comptime std.meta.trait.hasFn("parse")(Eff))
+            try Eff.parse(value)
+        else
+            @compileError("Invalid type " ++ @typeName(T));
+
+        return result;
+    } else {
+        // If param is present, but without an associated value
         return if (is_optional)
             null
         else if (T == bool)
@@ -238,8 +274,6 @@ fn parseQueryValue(alloc: std.mem.Allocator, comptime T: type, value: ?[]const u
         else
             error.InvalidValue;
     }
-
-    return try parseQueryValueNotNull(alloc, if (is_optional) std.meta.Child(T) else T, value.?);
 }
 
 const bool_map = std.ComptimeStringMap(bool, .{
@@ -256,32 +290,6 @@ const bool_map = std.ComptimeStringMap(bool, .{
     .{ "0", false },
 });
 
-fn parseQueryValueNotNull(alloc: std.mem.Allocator, comptime T: type, value: []const u8) !T {
-    const decoded = try decodeString(alloc, value);
-    errdefer alloc.free(decoded);
-
-    if (comptime std.meta.trait.isZigString(T)) return decoded;
-
-    defer alloc.free(decoded);
-
-    const result = if (comptime std.meta.trait.isIntegral(T))
-        try std.fmt.parseInt(T, decoded, 0)
-    else if (comptime std.meta.trait.isFloat(T))
-        try std.fmt.parseFloat(T, decoded)
-    else if (comptime std.meta.trait.is(.Enum)(T)) blk: {
-        _ = std.ascii.lowerString(decoded, decoded);
-        break :blk std.meta.stringToEnum(T, decoded) orelse return error.InvalidEnumValue;
-    } else if (T == bool) blk: {
-        _ = std.ascii.lowerString(decoded, decoded);
-        break :blk bool_map.get(decoded) orelse return error.InvalidBool;
-    } else if (comptime std.meta.trait.hasFn("parse")(T))
-        try T.parse(value)
-    else
-        @compileError("Invalid type " ++ @typeName(T));
-
-    return result;
-}
-
 fn isScalar(comptime T: type) bool {
     if (comptime std.meta.trait.isZigString(T)) return true;
     if (comptime std.meta.trait.isIntegral(T)) return true;
@@ -359,6 +367,69 @@ fn format(comptime prefix: []const u8, comptime name: []const u8, params: anytyp
 }
 
 test "parseQuery" {
+    const testCase = struct {
+        fn case(comptime T: type, expected: T, query_string: []const u8) !void {
+            const result = try parseQuery(std.testing.allocator, T, query_string);
+            defer parseQueryFree(std.testing.allocator, result);
+            try util.testing.expectDeepEqual(expected, result);
+        }
+    }.case;
+
+    try testCase(struct { int: usize = 3 }, .{ .int = 3 }, "");
+    try testCase(struct { int: usize = 3 }, .{ .int = 2 }, "int=2");
+    try testCase(struct { int: usize = 3 }, .{ .int = 2 }, "int=2&");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = false }, "");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = true }, "boolean");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = true }, "boolean=true");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = true }, "boolean=y");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = false }, "boolean=f");
+    try testCase(struct { boolean: bool = false }, .{ .boolean = false }, "boolean=no");
+    try testCase(struct { str_enum: ?enum { foo, bar } = null }, .{ .str_enum = null }, "");
+    try testCase(struct { str_enum: ?enum { foo, bar } = null }, .{ .str_enum = .foo }, "str_enum=foo");
+    try testCase(struct { str_enum: ?enum { foo, bar } = null }, .{ .str_enum = .bar }, "str_enum=bar");
+    try testCase(struct { str_enum: ?enum { foo, bar } = .foo }, .{ .str_enum = .foo }, "");
+    try testCase(struct { str_enum: ?enum { foo, bar } = .foo }, .{ .str_enum = null }, "str_enum");
+    try testCase(struct { n1: usize = 5, n2: usize = 5 }, .{ .n1 = 1, .n2 = 2 }, "n1=1&n2=2");
+    try testCase(struct { n1: usize = 5, n2: usize = 5 }, .{ .n1 = 1, .n2 = 2 }, "n1=1&n2=2&");
+    try testCase(struct { n1: usize = 5, n2: usize = 5 }, .{ .n1 = 1, .n2 = 2 }, "n1=1&&n2=2&");
+
+    try testCase(struct { str: ?[]const u8 = null }, .{ .str = null }, "");
+    try testCase(struct { str: ?[]const u8 = null }, .{ .str = null }, "str");
+    try testCase(struct { str: ?[]const u8 = null }, .{ .str = null }, "str=");
+    try testCase(struct { str: ?[]const u8 = null }, .{ .str = "foo" }, "str=foo");
+    try testCase(struct { str: ?[]const u8 = "foo" }, .{ .str = "foo" }, "str=foo");
+    try testCase(struct { str: ?[]const u8 = "foo" }, .{ .str = "foo" }, "");
+    try testCase(struct { str: ?[]const u8 = "foo" }, .{ .str = null }, "str");
+    try testCase(struct { str: ?[]const u8 = "foo" }, .{ .str = null }, "str=");
+
+    const rand_uuid = comptime util.Uuid.parse("c1fb6578-4d0c-4eb9-9f67-d56da3ae6f5d") catch unreachable;
+    try testCase(struct { id: ?util.Uuid = null }, .{ .id = null }, "");
+    try testCase(struct { id: ?util.Uuid = null }, .{ .id = null }, "id=");
+    try testCase(struct { id: ?util.Uuid = null }, .{ .id = null }, "id");
+    try testCase(struct { id: ?util.Uuid = null }, .{ .id = rand_uuid }, "id=" ++ rand_uuid.toCharArray());
+    try testCase(struct { id: ?util.Uuid = rand_uuid }, .{ .id = rand_uuid }, "");
+    try testCase(struct { id: ?util.Uuid = rand_uuid }, .{ .id = null }, "id=");
+    try testCase(struct { id: ?util.Uuid = rand_uuid }, .{ .id = null }, "id");
+    try testCase(struct { id: ?util.Uuid = rand_uuid }, .{ .id = rand_uuid }, "id=" ++ rand_uuid.toCharArray());
+
+    const SubStruct = struct {
+        sub: struct {
+            foo: usize = 1,
+            bar: usize = 2,
+        } = .{},
+    };
+    try testCase(SubStruct, .{ .sub = .{ .foo = 1, .bar = 2 } }, "");
+    try testCase(SubStruct, .{ .sub = .{ .foo = 3, .bar = 3 } }, "sub.foo=3&sub.bar=3");
+    try testCase(SubStruct, .{ .sub = .{ .foo = 3, .bar = 2 } }, "sub.foo=3");
+
+    // TODO: Semantics are ill-defined here
+    // const SubStruct2 = struct {
+    //     sub: ?struct {
+    //         foo: usize = 1,
+    //     } = null,
+    // };
+    // try testCase(SubStruct2, .{ .sub = null }, "");
+
     const TestQuery = struct {
         int: usize = 3,
         boolean: bool = false,
diff --git a/src/http/test.zig b/src/http/test.zig
index 1441ec2..c142f68 100644
--- a/src/http/test.zig
+++ b/src/http/test.zig
@@ -1,3 +1,5 @@
 test {
     _ = @import("./request/test_parser.zig");
+    _ = @import("./middleware.zig");
+    _ = @import("./query.zig");
 }
diff --git a/src/util/lib.zig b/src/util/lib.zig
index acc29f3..84b2122 100644
--- a/src/util/lib.zig
+++ b/src/util/lib.zig
@@ -160,6 +160,13 @@ pub fn deepClone(alloc: std.mem.Allocator, val: anytype) !@TypeOf(val) {
                 count += 1;
             }
         },
+        .Union => {
+            inline for (comptime std.meta.fieldNames(T)) |f| {
+                if (std.meta.isTag(val, f)) {
+                    return @unionInit(T, f, try deepClone(alloc, @field(val, f)));
+                }
+            } else unreachable;
+        },
         .Array => {
             var count: usize = 0;
             errdefer for (result[0..count]) |v| deepFree(alloc, v);