diff --git a/ts/state/ducks/calling.ts b/ts/state/ducks/calling.ts
index 602c338b96..0b57568009 100644
--- a/ts/state/ducks/calling.ts
+++ b/ts/state/ducks/calling.ts
@@ -914,7 +914,7 @@ function getExistingPeekInfo(
 }
 
 function removeConversationFromState(
-  state: CallingStateType,
+  state: Readonly<CallingStateType>,
   conversationId: string
 ): CallingStateType {
   return {
@@ -926,8 +926,8 @@ function removeConversationFromState(
 }
 
 export function reducer(
-  state: CallingStateType = getEmptyState(),
-  action: CallingActionType
+  state: Readonly<CallingStateType> = getEmptyState(),
+  action: Readonly<CallingActionType>
 ): CallingStateType {
   const { callsByConversation } = state;
 
diff --git a/ts/state/ducks/conversations.ts b/ts/state/ducks/conversations.ts
index 189003e70e..4012cb3fb7 100644
--- a/ts/state/ducks/conversations.ts
+++ b/ts/state/ducks/conversations.ts
@@ -811,8 +811,8 @@ function hasMessageHeightChanged(
 }
 
 export function reducer(
-  state: ConversationsStateType = getEmptyState(),
-  action: ConversationActionType
+  state: Readonly<ConversationsStateType> = getEmptyState(),
+  action: Readonly<ConversationActionType>
 ): ConversationsStateType {
   if (action.type === 'CONVERSATION_ADDED') {
     const { payload } = action;
diff --git a/ts/state/ducks/emojis.ts b/ts/state/ducks/emojis.ts
index 3308c7d1ee..98807be7a2 100644
--- a/ts/state/ducks/emojis.ts
+++ b/ts/state/ducks/emojis.ts
@@ -62,8 +62,8 @@ function getEmptyState(): EmojisStateType {
 }
 
 export function reducer(
-  state: EmojisStateType = getEmptyState(),
-  action: EmojisActionType
+  state: Readonly<EmojisStateType> = getEmptyState(),
+  action: Readonly<EmojisActionType>
 ): EmojisStateType {
   if (action.type === 'emojis/USE_EMOJI') {
     const { payload } = action;
diff --git a/ts/state/ducks/expiration.ts b/ts/state/ducks/expiration.ts
index 76a175129b..7215023cfc 100644
--- a/ts/state/ducks/expiration.ts
+++ b/ts/state/ducks/expiration.ts
@@ -40,8 +40,8 @@ function getEmptyState(): ExpirationStateType {
 }
 
 export function reducer(
-  state: ExpirationStateType = getEmptyState(),
-  action: ExpirationActionType
+  state: Readonly<ExpirationStateType> = getEmptyState(),
+  action: Readonly<ExpirationActionType>
 ): ExpirationStateType {
   if (action.type === HYDRATE_EXPIRATION_STATUS) {
     return {
diff --git a/ts/state/ducks/items.ts b/ts/state/ducks/items.ts
index 6699dabae9..d6dc400625 100644
--- a/ts/state/ducks/items.ts
+++ b/ts/state/ducks/items.ts
@@ -109,8 +109,8 @@ function getEmptyState(): ItemsStateType {
 }
 
 export function reducer(
-  state: ItemsStateType = getEmptyState(),
-  action: ItemsActionType
+  state: Readonly<ItemsStateType> = getEmptyState(),
+  action: Readonly<ItemsActionType>
 ): ItemsStateType {
   if (action.type === 'items/PUT_EXTERNAL') {
     const { payload } = action;
diff --git a/ts/state/ducks/network.ts b/ts/state/ducks/network.ts
index 69b7ea6efc..2406e3a055 100644
--- a/ts/state/ducks/network.ts
+++ b/ts/state/ducks/network.ts
@@ -83,8 +83,8 @@ function getEmptyState(): NetworkStateType {
 }
 
 export function reducer(
-  state: NetworkStateType = getEmptyState(),
-  action: NetworkActionType
+  state: Readonly<NetworkStateType> = getEmptyState(),
+  action: Readonly<NetworkActionType>
 ): NetworkStateType {
   if (action.type === CHECK_NETWORK_STATUS) {
     const { isOnline, socketStatus } = action.payload;
diff --git a/ts/state/ducks/safetyNumber.ts b/ts/state/ducks/safetyNumber.ts
index 0951476f6d..e23f3998ff 100644
--- a/ts/state/ducks/safetyNumber.ts
+++ b/ts/state/ducks/safetyNumber.ts
@@ -163,8 +163,8 @@ function getEmptyState(): SafetyNumberStateType {
 }
 
 export function reducer(
-  state: SafetyNumberStateType = getEmptyState(),
-  action: SafetyNumberActionType
+  state: Readonly<SafetyNumberStateType> = getEmptyState(),
+  action: Readonly<SafetyNumberActionType>
 ): SafetyNumberStateType {
   if (action.type === TOGGLE_VERIFIED_PENDING) {
     const { contact } = action.payload;
diff --git a/ts/state/ducks/search.ts b/ts/state/ducks/search.ts
index 8083851b58..d74e09c71e 100644
--- a/ts/state/ducks/search.ts
+++ b/ts/state/ducks/search.ts
@@ -337,8 +337,8 @@ function getEmptyState(): SearchStateType {
 }
 
 export function reducer(
-  state: SearchStateType = getEmptyState(),
-  action: SearchActionType
+  state: Readonly<SearchStateType> = getEmptyState(),
+  action: Readonly<SearchActionType>
 ): SearchStateType {
   if (action.type === 'SHOW_ARCHIVED_CONVERSATIONS') {
     return getEmptyState();
diff --git a/ts/state/ducks/stickers.ts b/ts/state/ducks/stickers.ts
index 8d13e8322a..27bee852d2 100644
--- a/ts/state/ducks/stickers.ts
+++ b/ts/state/ducks/stickers.ts
@@ -373,8 +373,8 @@ function getEmptyState(): StickersStateType {
 }
 
 export function reducer(
-  state: StickersStateType = getEmptyState(),
-  action: StickersActionType
+  state: Readonly<StickersStateType> = getEmptyState(),
+  action: Readonly<StickersActionType>
 ): StickersStateType {
   if (action.type === 'stickers/STICKER_PACK_ADDED') {
     // ts complains due to `stickers: {}` being overridden by the payload
diff --git a/ts/state/ducks/updates.ts b/ts/state/ducks/updates.ts
index 048bdd3163..9bd20446ff 100644
--- a/ts/state/ducks/updates.ts
+++ b/ts/state/ducks/updates.ts
@@ -111,8 +111,8 @@ function getEmptyState(): UpdatesStateType {
 }
 
 export function reducer(
-  state: UpdatesStateType = getEmptyState(),
-  action: UpdatesActionType
+  state: Readonly<UpdatesStateType> = getEmptyState(),
+  action: Readonly<UpdatesActionType>
 ): UpdatesStateType {
   if (action.type === SHOW_UPDATE_DIALOG) {
     return {
diff --git a/ts/state/ducks/user.ts b/ts/state/ducks/user.ts
index b025aee363..3e488f9630 100644
--- a/ts/state/ducks/user.ts
+++ b/ts/state/ducks/user.ts
@@ -83,8 +83,8 @@ function getEmptyState(): UserStateType {
 }
 
 export function reducer(
-  state: UserStateType = getEmptyState(),
-  action: UserActionType
+  state: Readonly<UserStateType> = getEmptyState(),
+  action: Readonly<UserActionType>
 ): UserStateType {
   if (!state) {
     return getEmptyState();