diff --git a/internal/statetransition/errors.go b/internal/statetransition/errors.go
index 1c8d4f9..aba949f 100644
--- a/internal/statetransition/errors.go
+++ b/internal/statetransition/errors.go
@@ -5,10 +5,10 @@ import "github.com/pkg/errors"
 var (
 	ErrTimeslotOutOfRange   = errors.New("timeslot out of range")
 	ErrWrongAssignment      = errors.New("wrong assignment")
-	ErrBadSignature         = errors.New("bad_signature")
-	ErrReportTimeout        = errors.New("report_timeout")
-	ErrBadAttestationParent = errors.New("bad_attestation_parent")
-	ErrBadOrder             = errors.New("bad_order")
-	ErrCoreNotEngaged       = errors.New("core_not_engaged")
-	ErrBadValidatorIndex    = errors.New("bad_validator_index")
+	ErrBadSignature         = errors.New("bad signature")
+	ErrReportTimeout        = errors.New("report timeout")
+	ErrBadAttestationParent = errors.New("bad attestation parent")
+	ErrBadOrder             = errors.New("bad order")
+	ErrCoreNotEngaged       = errors.New("core not engaged")
+	ErrBadValidatorIndex    = errors.New("bad validator index")
 )
diff --git a/tests/integration/assurances_test.go b/tests/integration/assurances_test.go
index ead3408..787e5a1 100644
--- a/tests/integration/assurances_test.go
+++ b/tests/integration/assurances_test.go
@@ -192,7 +192,7 @@ func TestAssurancesTiny(t *testing.T) {
 			newBlock := mapBlock(tc.Input)
 			theState := mapAssurancesState(tc.PreState)
 			if theState.CoreAssignments, err = statetransition.CalculateIntermediateCoreFromAssurances(theState.ValidatorState.CurrentValidators, theState.CoreAssignments, newBlock.Header, newBlock.Extrinsic.EA); tc.Output.Err != "" {
-				assert.EqualError(t, err, tc.Output.Err)
+				require.EqualError(t, err, strings.ReplaceAll(tc.Output.Err, "_", " "))
 			} else {
 				require.NoError(t, err)
 			}