diff --git a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
index 8b2e39716..58002a5e8 100644
--- a/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
+++ b/Signal/src/ViewControllers/ConversationView/ConversationViewController.m
@@ -544,6 +544,9 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
     keyboardOnViewAppearing:(BOOL)keyboardOnViewAppearing
         callOnViewAppearing:(BOOL)callOnViewAppearing
 {
+    // At most one.
+    OWSAssert(!keyboardOnViewAppearing || !callOnViewAppearing);
+
     if (callOnViewAppearing) {
         keyboardOnViewAppearing = NO;
     }
diff --git a/Signal/src/ViewControllers/HomeViewController.m b/Signal/src/ViewControllers/HomeViewController.m
index e45432411..7555d1d0b 100644
--- a/Signal/src/ViewControllers/HomeViewController.m
+++ b/Signal/src/ViewControllers/HomeViewController.m
@@ -743,6 +743,9 @@ typedef NS_ENUM(NSInteger, CellState) { kArchiveState, kInboxState };
     keyboardOnViewAppearing:(BOOL)keyboardOnViewAppearing
         callOnViewAppearing:(BOOL)callOnViewAppearing
 {
+    // At most one.
+    OWSAssert(!keyboardOnViewAppearing || !callOnViewAppearing);
+
     if (thread == nil) {
         OWSFail(@"Thread unexpectedly nil");
         return;
diff --git a/Signal/src/environment/Environment.m b/Signal/src/environment/Environment.m
index 30e01c23b..164352e21 100644
--- a/Signal/src/environment/Environment.m
+++ b/Signal/src/environment/Environment.m
@@ -200,6 +200,9 @@ static Environment *environment = nil;
                   keyboardOnViewAppearing:(BOOL)keyboardOnViewAppearing
                       callOnViewAppearing:(BOOL)callOnViewAppearing
 {
+    // At most one.
+    OWSAssert(!keyboardOnViewAppearing || !callOnViewAppearing);
+
     DispatchMainThreadSafe(^{
         __block TSThread *thread = nil;
         [[TSStorageManager sharedManager].dbReadWriteConnection
@@ -221,6 +224,9 @@ static Environment *environment = nil;
              keyboardOnViewAppearing:(BOOL)keyboardOnViewAppearing
                  callOnViewAppearing:(BOOL)callOnViewAppearing
 {
+    // At most one.
+    OWSAssert(!keyboardOnViewAppearing || !callOnViewAppearing);
+
     if (!thread) {
         OWSFail(@"%@ Can't present nil thread.", self.tag);
         return;