diff --git a/diff/parameters_diff_by_location.go b/diff/parameters_diff_by_location.go
index 5585d7ff..55ee44e1 100644
--- a/diff/parameters_diff_by_location.go
+++ b/diff/parameters_diff_by_location.go
@@ -34,11 +34,7 @@ type ParamNamesByLocation map[string]utils.StringList
 
 // Len returns the number of all params in all locations
 func (params ParamNamesByLocation) Len() int {
-	result := 0
-	for _, l := range params {
-		result += l.Len()
-	}
-	return result
+	return lenNested(params)
 }
 
 // ParamDiffByLocation maps param location (path, query, header or cookie) to param diffs in this location
@@ -46,8 +42,12 @@ type ParamDiffByLocation map[string]ParamDiffs
 
 // Len returns the number of all params in all locations
 func (params ParamDiffByLocation) Len() int {
+	return lenNested(params)
+}
+
+func lenNested[T utils.StringList | ParamDiffs](mapOfList map[string]T) int {
 	result := 0
-	for _, l := range params {
+	for _, l := range mapOfList {
 		result += len(l)
 	}
 	return result
diff --git a/diff/parameters_diff_by_location_test.go b/diff/parameters_diff_by_location_test.go
new file mode 100644
index 00000000..d68e5db3
--- /dev/null
+++ b/diff/parameters_diff_by_location_test.go
@@ -0,0 +1,23 @@
+package diff_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/tufin/oasdiff/diff"
+	"github.com/tufin/oasdiff/utils"
+)
+
+func TestParamNamesByLocation_Len(t *testing.T) {
+	require.Equal(t, 3, diff.ParamNamesByLocation{
+		"query":  utils.StringList{"name"},
+		"header": utils.StringList{"id", "organization"},
+	}.Len())
+}
+
+func TestParamDiffByLocation_Len(t *testing.T) {
+	require.Equal(t, 3, diff.ParamDiffByLocation{
+		"query":  diff.ParamDiffs{"query": &diff.ParameterDiff{}},
+		"header": diff.ParamDiffs{"id": &diff.ParameterDiff{}, "organization": &diff.ParameterDiff{}},
+	}.Len())
+}