diff --git a/cast_test.go b/cast_test.go
index dac77d7..b665b94 100644
--- a/cast_test.go
+++ b/cast_test.go
@@ -952,6 +952,8 @@ func TestToStringMapTimeDuration(t *testing.T) {
 	var stringMapInterface = map[string]interface{}{"key 1": "5m", "key 2": "10h", "key 3": "1h15m30.918273645s"}
 	var interfaceMapString = map[interface{}]string{"key 1": "5m", "key 2": "10h", "key 3": "1h15m30.918273645s"}
 	var interfaceMapInterface = map[interface{}]interface{}{"key 1": "5m", "key 2": "10h", "key 3": "1h15m30.918273645s"}
+	var jsonString = `{"key 1": "5m", "key 2": "10h", "key 3": "1h15m30.918273645s"}`
+	var invalidJsonString = `{"key 1": "5m", "key 2": "10h", "key 3": "1h15m30.918273645s"`
 	var emptyString = ""
 
 	tests := []struct {
@@ -963,11 +965,13 @@ func TestToStringMapTimeDuration(t *testing.T) {
 		{stringMapInterface, expectResult, false},
 		{interfaceMapString, expectResult, false},
 		{interfaceMapInterface, expectResult, false},
+		{jsonString, expectResult, false},
 
 		// errors
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{emptyString, nil, true},
+		{invalidJsonString, nil, true},
 	}
 
 	for i, test := range tests {
@@ -975,7 +979,7 @@ func TestToStringMapTimeDuration(t *testing.T) {
 
 		v, err := ToStringMapTimeDurationE(test.input)
 		if test.iserr {
-			assert.Error(t, err, errmsg)
+			assert.Error(t, err, errmsg, test)
 			continue
 		}
 
diff --git a/caste.go b/caste.go
index 8f91355..7b0df0c 100644
--- a/caste.go
+++ b/caste.go
@@ -1103,6 +1103,12 @@ func ToStringMapTimeDurationE(i interface{}) (map[string]time.Duration, error) {
 			m[ToString(k)] = ToDuration(val)
 		}
 		return m, nil
+	case string:
+		m2, err := ToStringMapStringE(i)
+		if err != nil || m2 == nil {
+			return m, err
+		}
+		return ToStringMapTimeDurationE(m2)
 	default:
 		return m, fmt.Errorf("unable to cast %#v of type %T to map[string]time.Duration", i, i)
 	}