diff --git a/src/bun.js/api/bun/socket.zig b/src/bun.js/api/bun/socket.zig
index 44bc2a370d0e6..f2b4d59d4b607 100644
--- a/src/bun.js/api/bun/socket.zig
+++ b/src/bun.js/api/bun/socket.zig
@@ -3066,6 +3066,11 @@ fn NewSocket(comptime ssl: bool) type {
             if (this.socket.isDetached() or this.socket.isNamedPipe()) {
                 return JSValue.jsUndefined();
             }
+            if (this.handlers.is_server) {
+                globalObject.throw("Cannot upgrade a server-side socket", .{});
+                return .zero;
+            }
+
             const args = callframe.arguments(1);
 
             if (args.len < 1) {