diff --git a/tests/testtypes/consensus-spec-tests/gen_bits_struct_ssz.go b/tests/testtypes/consensus-spec-tests/gen_bits_struct_ssz.go
index 1115077..884417d 100644
--- a/tests/testtypes/consensus-spec-tests/gen_bits_struct_ssz.go
+++ b/tests/testtypes/consensus-spec-tests/gen_bits_struct_ssz.go
@@ -6,13 +6,13 @@ import "github.com/karalabe/ssz"
 
 // SizeSSZ returns either the static size of the object if fixed == true, or
 // the total size otherwise.
-func (obj *BitsStruct) SizeSSZ(fixed bool) uint32 {
-	var size = uint32(4 + 1 + 1 + 4 + 1)
+func (obj *BitsStruct) SizeSSZ(sizer *ssz.Sizer, fixed bool) (size uint32) {
+	size = 4 + 1 + 1 + 4 + 1
 	if fixed {
 		return size
 	}
-	size += ssz.SizeSliceOfBits(obj.A)
-	size += ssz.SizeSliceOfBits(obj.D)
+	size += ssz.SizeSliceOfBits(sizer, obj.A)
+	size += ssz.SizeSliceOfBits(sizer, obj.D)
 
 	return size
 }
diff --git a/tests/testtypes/consensus-spec-tests/gen_fixed_test_struct_ssz.go b/tests/testtypes/consensus-spec-tests/gen_fixed_test_struct_ssz.go
index cfebc25..c9c5f25 100644
--- a/tests/testtypes/consensus-spec-tests/gen_fixed_test_struct_ssz.go
+++ b/tests/testtypes/consensus-spec-tests/gen_fixed_test_struct_ssz.go
@@ -5,7 +5,7 @@ package consensus_spec_tests
 import "github.com/karalabe/ssz"
 
 // SizeSSZ returns the total size of the static ssz object.
-func (obj *FixedTestStruct) SizeSSZ() uint32 {
+func (obj *FixedTestStruct) SizeSSZ(sizer *ssz.Sizer) uint32 {
 	return 1 + 8 + 4
 }
 
diff --git a/tests/testtypes/consensus-spec-tests/gen_single_field_test_struct_ssz.go b/tests/testtypes/consensus-spec-tests/gen_single_field_test_struct_ssz.go
index 4790439..a101db8 100644
--- a/tests/testtypes/consensus-spec-tests/gen_single_field_test_struct_ssz.go
+++ b/tests/testtypes/consensus-spec-tests/gen_single_field_test_struct_ssz.go
@@ -5,7 +5,7 @@ package consensus_spec_tests
 import "github.com/karalabe/ssz"
 
 // SizeSSZ returns the total size of the static ssz object.
-func (obj *SingleFieldTestStruct) SizeSSZ() uint32 {
+func (obj *SingleFieldTestStruct) SizeSSZ(sizer *ssz.Sizer) uint32 {
 	return 1
 }
 
diff --git a/tests/testtypes/consensus-spec-tests/gen_small_test_struct_ssz.go b/tests/testtypes/consensus-spec-tests/gen_small_test_struct_ssz.go
index 020e433..8191ad5 100644
--- a/tests/testtypes/consensus-spec-tests/gen_small_test_struct_ssz.go
+++ b/tests/testtypes/consensus-spec-tests/gen_small_test_struct_ssz.go
@@ -5,7 +5,7 @@ package consensus_spec_tests
 import "github.com/karalabe/ssz"
 
 // SizeSSZ returns the total size of the static ssz object.
-func (obj *SmallTestStruct) SizeSSZ() uint32 {
+func (obj *SmallTestStruct) SizeSSZ(sizer *ssz.Sizer) uint32 {
 	return 2 + 2
 }
 
diff --git a/tests/testtypes/consensus-spec-tests/types_monoliths.go b/tests/testtypes/consensus-spec-tests/types_monoliths.go
index c9ab5f0..153526f 100644
--- a/tests/testtypes/consensus-spec-tests/types_monoliths.go
+++ b/tests/testtypes/consensus-spec-tests/types_monoliths.go
@@ -6,10 +6,10 @@ package consensus_spec_tests
 
 import "github.com/holiman/uint256"
 
-//go:generate go run ../../../cmd/sszgen -type ExecutionPayloadMonolith -out gen_execution_payload_monolith_ssz.go
-//go:generate go run ../../../cmd/sszgen -type ExecutionPayloadHeaderMonolith -out gen_execution_payload_header_monolith_ssz.go
-//go:generate go run ../../../cmd/sszgen -type BeaconBlockBodyMonolith -out gen_beacon_block_body_monolith_ssz.go
-//go:generate go run ../../../cmd/sszgen -type BeaconStateMonolith -out gen_beacon_state_monolith_ssz.go
+//go:generate go run -cover ../../../cmd/sszgen -type ExecutionPayloadMonolith -out gen_execution_payload_monolith_ssz.go
+//go:generate go run -cover ../../../cmd/sszgen -type ExecutionPayloadHeaderMonolith -out gen_execution_payload_header_monolith_ssz.go
+//go:generate go run -cover ../../../cmd/sszgen -type BeaconBlockBodyMonolith -out gen_beacon_block_body_monolith_ssz.go
+//go:generate go run -cover ../../../cmd/sszgen -type BeaconStateMonolith -out gen_beacon_state_monolith_ssz.go
 
 type BeaconBlockBodyMonolith struct {
 	RandaoReveal          [96]byte