diff --git a/src/muz/base/fixedpoint_params.pyg b/src/muz/base/fixedpoint_params.pyg
index b32f1f586..7b8f8fb72 100644
--- a/src/muz/base/fixedpoint_params.pyg
+++ b/src/muz/base/fixedpoint_params.pyg
@@ -181,11 +181,11 @@ def_module_params('fixedpoint',
                           ('spacer.keep_proxy', BOOL, True, 'keep proxy variables (internal parameter)'),
                           ('spacer.q3.instantiate', BOOL, True, 'instantiate quantified lemmas'),
                           ('spacer.q3', BOOL, True, 'allow quantified lemmas in frames'),
-                          ('spacer.iuc', UINT, 0,
+                          ('spacer.iuc', UINT, 1,
                            '0 = use old implementation of unsat-core-generation, ' +
                            '1 = use new implementation of IUC generation, ' +
                            '2 = use new implementation of IUC + min-cut optimization'),
-                          ('spacer.iuc.arith', UINT, 0,
+                          ('spacer.iuc.arith', UINT, 1,
                            '0 = use simple Farkas plugin, ' +
                            '1 = use simple Farkas plugin with constant from other partition (like old unsat-core-generation),' +
                            '2 = use Gaussian elimination optimization (broken), 3 = use additive IUC plugin'),