diff --git a/Server-Protocol-Buffer/src/main/proto/internal/ppdd/ppa_data.proto b/Server-Protocol-Buffer/src/main/proto/internal/ppdd/ppa_data.proto
index 412ab95c88ed0e69061952cafe6954ad0b3379f9..0299c63493ea47a508fd3894e57a7ae6e1b67470 100644
--- a/Server-Protocol-Buffer/src/main/proto/internal/ppdd/ppa_data.proto
+++ b/Server-Protocol-Buffer/src/main/proto/internal/ppdd/ppa_data.proto
@@ -2,6 +2,7 @@
 syntax = "proto3";
 package de.rki.coronawarnapp.server.protocols.internal.ppdd;
 
+import "internal/ppdd/tri_state_boolean.proto";
 
 message PPADataIOS {
 
@@ -92,7 +93,7 @@ message PPAKeySubmissionMetadata {
   int32 ptDaysSinceMostRecentDateAtRiskLevelAtTestRegistration = 13;
   int32 ptHoursSinceHighRiskWarningAtTestRegistration = 14;
 
-  bool submittedWithCheckIns = 15;
+  TriStateBoolean submittedWithCheckIns = 15;
 }
 
 enum PPARiskLevel {
diff --git a/Server-Protocol-Buffer/src/main/proto/internal/ppdd/tri_state_boolean.proto b/Server-Protocol-Buffer/src/main/proto/internal/ppdd/tri_state_boolean.proto
new file mode 100644
index 0000000000000000000000000000000000000000..24eb4b9af9935b1c986bc27b86c9b90e90f62800
--- /dev/null
+++ b/Server-Protocol-Buffer/src/main/proto/internal/ppdd/tri_state_boolean.proto
@@ -0,0 +1,10 @@
+// This file is auto-generated, DO NOT make any changes here
+syntax = "proto3";
+package de.rki.coronawarnapp.server.protocols.internal.ppdd;
+
+
+enum TriStateBoolean {
+  TSB_UNSPECIFIED = 0;
+  TSB_TRUE = 1;
+  TSB_FALSE = 2;
+}
\ No newline at end of file