diff --git a/src/special/build_runner.zig b/src/special/build_runner.zig
index f6b0549..0106e98 100644
--- a/src/special/build_runner.zig
+++ b/src/special/build_runner.zig
@@ -60,7 +60,7 @@ fn processPackage(out_stream: anytype, pkg: Pkg) anyerror!void {
 }
 
 fn runBuild(builder: *Builder) anyerror!void {
-    switch (@typeInfo(@TypeOf(root.build).ReturnType)) {
+    switch (@typeInfo(@typeInfo(@TypeOf(root.build)).Fn.return_type.?)) {
         .Void => root.build(builder),
         .ErrorUnion => try root.build(builder),
         else => @compileError("expected return type of build to be 'void' or '!void'"),