diff --git a/activities.go b/activities.go
index e5e2989..2ddf0f9 100644
--- a/activities.go
+++ b/activities.go
@@ -2,6 +2,7 @@ package libwekan
 
 import (
 	"context"
+	"go.mongodb.org/mongo-driver/mongo"
 	"go.mongodb.org/mongo-driver/mongo/options"
 	"time"
 
@@ -215,6 +216,9 @@ func (wekan *Wekan) GetActivityFromID(ctx context.Context, activityID ActivityID
 	var activity Activity
 	err := wekan.db.Collection("activities").FindOne(ctx, bson.M{"_id": activityID}).Decode(&activity)
 	if err != nil {
+		if err == mongo.ErrNoDocuments {
+			return Activity{}, ActivityNotFoundError{string(activityID)}
+		}
 		return Activity{}, UnexpectedMongoError{err}
 	}
 	return activity, nil
diff --git a/activities_integration_test.go b/activities_integration_test.go
index 42e9872..0bbf20c 100644
--- a/activities_integration_test.go
+++ b/activities_integration_test.go
@@ -105,8 +105,8 @@ func TestActivities_GetActivityFromID_WhenActivityDoesntExist(t *testing.T) {
 	// THEN
 	ass.Empty(actualActivityFromMethod)
 	ass.Empty(actualActivityFromID)
-	ass.IsType(UnknownActivityError{}, errFromMethod)
-	ass.IsType(UnknownActivityError{}, errFromID)
+	ass.IsType(ActivityNotFoundError{}, errFromMethod)
+	ass.IsType(ActivityNotFoundError{}, errFromID)
 }
 
 func TestActivities_CheckActivityFromID(t *testing.T) {
@@ -128,5 +128,5 @@ func TestActivities_CheckActivityFromID_WhenActivityDoesntExist(t *testing.T) {
 	activityID := ActivityID(t.Name() + "absent")
 
 	// THEN
-	ass.IsType(UnknownActivityError{}, activityID.Check(ctx, &wekan))
+	ass.IsType(ActivityNotFoundError{}, activityID.Check(ctx, &wekan))
 }
diff --git a/errors.go b/errors.go
index 9a69784..a35313b 100644
--- a/errors.go
+++ b/errors.go
@@ -218,11 +218,11 @@ func (e NothingDoneError) Error() string {
 	return "le traitement n'a eu aucun effet"
 }
 
-type UnknownActivityError struct {
+type ActivityNotFoundError struct {
 	key string
 }
 
-func (e UnknownActivityError) Error() string {
+func (e ActivityNotFoundError) Error() string {
 	return fmt.Sprintf("l'activité n'existe pas (ID: %s)", e.key)
 }
 
diff --git a/errors_test.go b/errors_test.go
index 9e07df7..cae31d3 100644
--- a/errors_test.go
+++ b/errors_test.go
@@ -135,7 +135,7 @@ func TestErrors_NothingDoneError(t *testing.T) {
 	assert.EqualError(t, e, expected)
 }
 func TestErrors_UnknownActivityError(t *testing.T) {
-	e := UnknownActivityError{"test"}
+	e := ActivityNotFoundError{"test"}
 	expected := fmt.Sprintf("l'activité n'existe pas (ID: %s)", e.key)
 	assert.EqualError(t, e, expected)
 }