diff --git a/client/src/activity.vala b/client/src/activity.vala
index 11a3429..ed42137 100644
--- a/client/src/activity.vala
+++ b/client/src/activity.vala
@@ -7,7 +7,9 @@ namespace StudySystemClient {
 
 	public enum ActivityType {
 		READING = 0,
-		EXERCISES = 1;
+		EXERCISES = 1,
+
+		COUNT;
 
 		public string to_string() {
 			switch (this) {
diff --git a/client/src/response.vala b/client/src/response.vala
index ad0c3db..4baa4d9 100644
--- a/client/src/response.vala
+++ b/client/src/response.vala
@@ -67,7 +67,9 @@ namespace StudySystemClient.Response {
 		public enum Value {
 			INVALID_REQUEST = 0,
 			INVALID_ARGUMENTS = 1,
-			SERVER_ERROR = 2;
+			SERVER_ERROR = 2,
+
+			COUNT;
 
 			public string to_string() {
 				switch (this) {
@@ -91,9 +93,9 @@ namespace StudySystemClient.Response {
 				throw new DecodeError.INVALID_BODY(
 					"Error was not an ENUMERATED");
 			}
-			if (enumerated.value < 0 || enumerated.value > 2) {
+			if (enumerated.value < 0 || enumerated.value >= Value.COUNT) {
 				throw new DecodeError.INVALID_BODY(
-					"Error type was not in range 0..2");
+					"Error type was not in range 0..$(Value.COUNT)");
 			}
 			value = (Value)enumerated.value;
 		}
@@ -162,7 +164,7 @@ namespace StudySystemClient.Response {
 			string name, Der.Datum datum) throws DecodeError {
 			if (datum is Der.Enumerated) {
 				var value = datum.value;
-				if (0 <= value <= 1)
+				if (0 <= value < ActivityType.COUNT)
 					return (ActivityType)value;
 				throw new DecodeError.INVALID_BODY(
 					"Invalid value for ActivityType: %lld", value);