Index: libcfa/src/concurrency/io/setup.cfa
===================================================================
--- libcfa/src/concurrency/io/setup.cfa	(revision 2606a033886574e16a9cb5dc08e8939c258ac86a)
+++ libcfa/src/concurrency/io/setup.cfa	(revision 63fe427cd6b6ea38a3ca460dd560e4901b87029b)
@@ -298,5 +298,11 @@
 		if( params_in.poll_complete ) params.flags |= IORING_SETUP_IOPOLL;
 
-		uint32_t nentries = params_in.num_entries;
+		uint32_t nentries = params_in.num_entries != 0 ? params_in.num_entries : 256;
+		if( !is_pow2(nentries) ) {
+			abort("ERROR: I/O setup 'num_entries' must be a power of 2\n");
+		}
+		if( params_in.poller_submits && params_in.eager_submits ) {
+			abort("ERROR: I/O setup 'poller_submits' and 'eager_submits' cannot be used together\n");
+		}
 
 		int fd = syscall(__NR_io_uring_setup, nentries, &params );