diff --git a/src/addons/mod/assign/submission/onlinetext/component/onlinetext.ts b/src/addons/mod/assign/submission/onlinetext/component/onlinetext.ts
index d9f32b708..ca9afe172 100644
--- a/src/addons/mod/assign/submission/onlinetext/component/onlinetext.ts
+++ b/src/addons/mod/assign/submission/onlinetext/component/onlinetext.ts
@@ -111,7 +111,7 @@ export class AddonModAssignSubmissionOnlineTextComponent extends AddonModAssignS
      *
      * @param text The new text.
      */
-    onChange(text: string): void {
+    onChange(text?: string | null): void {
         // Count words if needed.
         if (this.wordLimitEnabled) {
             // Cancel previous wait.
diff --git a/src/addons/mod/forum/components/post/post.ts b/src/addons/mod/forum/components/post/post.ts
index c2f1d5e80..8024b9c25 100644
--- a/src/addons/mod/forum/components/post/post.ts
+++ b/src/addons/mod/forum/components/post/post.ts
@@ -332,8 +332,8 @@ export class AddonModForumPostComponent implements OnInit, OnDestroy, OnChanges
      *
      * @param text The new text.
      */
-    onMessageChange(text: string): void {
-        this.formData.message = text;
+    onMessageChange(text?: string | null): void {
+        this.formData.message = text ?? '';
     }
 
     /**
diff --git a/src/addons/mod/forum/pages/new-discussion/new-discussion.ts b/src/addons/mod/forum/pages/new-discussion/new-discussion.ts
index 6978faa24..df9003480 100644
--- a/src/addons/mod/forum/pages/new-discussion/new-discussion.ts
+++ b/src/addons/mod/forum/pages/new-discussion/new-discussion.ts
@@ -511,8 +511,8 @@ export class AddonModForumNewDiscussionPage implements OnInit, OnDestroy, CanLea
      *
      * @param text The new text.
      */
-    onMessageChange(text: string): void {
-        this.newDiscussion.message = text;
+    onMessageChange(text?: string | null): void {
+        this.newDiscussion.message = text ?? '';
     }
 
     /**
diff --git a/src/addons/mod/glossary/pages/edit/edit.ts b/src/addons/mod/glossary/pages/edit/edit.ts
index 882f51daa..d5d9a3ed8 100644
--- a/src/addons/mod/glossary/pages/edit/edit.ts
+++ b/src/addons/mod/glossary/pages/edit/edit.ts
@@ -173,8 +173,8 @@ export class AddonModGlossaryEditPage implements OnInit, CanLeave {
      *
      * @param text The new text.
      */
-    onDefinitionChange(text: string): void {
-        this.data.definition = text;
+    onDefinitionChange(text?: string | null): void {
+        this.data.definition = text ?? '';
     }
 
     /**
diff --git a/src/addons/mod/workshop/components/assessment-strategy/assessment-strategy.ts b/src/addons/mod/workshop/components/assessment-strategy/assessment-strategy.ts
index e2ea393c4..90afcbac2 100644
--- a/src/addons/mod/workshop/components/assessment-strategy/assessment-strategy.ts
+++ b/src/addons/mod/workshop/components/assessment-strategy/assessment-strategy.ts
@@ -403,8 +403,8 @@ export class AddonModWorkshopAssessmentStrategyComponent implements OnInit, OnDe
      *
      * @param text The new text.
      */
-    onFeedbackChange(text: string): void {
-        this.feedbackText = text;
+    onFeedbackChange(text?: string | null): void {
+        this.feedbackText = text ?? '';
     }
 
     /**
diff --git a/src/core/services/utils/text.ts b/src/core/services/utils/text.ts
index 23596a41f..55c2b5fb5 100644
--- a/src/core/services/utils/text.ts
+++ b/src/core/services/utils/text.ts
@@ -332,7 +332,7 @@ export class CoreTextUtilsProvider {
      * @param text Text to count.
      * @returns Number of words.
      */
-    countWords(text: string): number {
+    countWords(text?: string | null): number {
         if (!text || typeof text != 'string') {
             return 0;
         }