diff --git a/src/assets/lang/en.json b/src/assets/lang/en.json
index 391cb9b50..70be9851c 100644
--- a/src/assets/lang/en.json
+++ b/src/assets/lang/en.json
@@ -1861,6 +1861,7 @@
     "core.mainmenu.help": "Help",
     "core.mainmenu.logout": "Log out",
     "core.mainmenu.website": "Website",
+    "core.maxfilesize": "Maximum size for new files: {{$a}}",
     "core.maxsizeandattachments": "Maximum file size: {{$a.size}}, maximum number of files: {{$a.attachments}}",
     "core.min": "min",
     "core.mins": "mins",
diff --git a/src/components/attachments/attachments.ts b/src/components/attachments/attachments.ts
index 810165c39..e327db8a6 100644
--- a/src/components/attachments/attachments.ts
+++ b/src/components/attachments/attachments.ts
@@ -39,8 +39,8 @@ import { CoreFileUploaderHelperProvider } from '@core/fileuploader/providers/hel
 })
 export class CoreAttachmentsComponent implements OnInit {
     @Input() files: any[]; // List of attachments. New attachments will be added to this array.
-    @Input() maxSize: number; // Max size for attachments. If not defined, 0 or -1, unknown size.
-    @Input() maxSubmissions: number; // Max number of attachments. If -1 or not defined, unknown limit.
+    @Input() maxSize: number; // Max size for attachments. -1 means unlimited, not defined or 0 means unknown limit.
+    @Input() maxSubmissions: number; // Max number of attachments. -1 means unlimited, not defined means unknown limit.
     @Input() component: string; // Component the downloaded files will be linked to.
     @Input() componentId: string | number; // Component ID.
     @Input() allowOffline: boolean | string; // Whether to allow selecting files in offline.
@@ -61,17 +61,18 @@ export class CoreAttachmentsComponent implements OnInit {
      * Component being initialized.
      */
     ngOnInit(): void {
-        this.maxSize = Number(this.maxSize); // Make sure it's defined and it's a number.
-        this.maxSize = !isNaN(this.maxSize) && this.maxSize > 0 ? this.maxSize : -1;
+        this.maxSize = Number(this.maxSize) || 0; // Make sure it's defined and it's a number.
 
-        if (this.maxSize == -1) {
+        if (this.maxSize === 0) {
             this.maxSizeReadable = this.translate.instant('core.unknown');
-        } else {
+        } else if (this.maxSize > 0) {
             this.maxSizeReadable = this.textUtils.bytesToSize(this.maxSize, 2);
+        } else {
+            this.maxSizeReadable = this.translate.instant('core.unlimited');
         }
 
         if (typeof this.maxSubmissions == 'undefined' || this.maxSubmissions < 0) {
-            this.maxSubmissionsReadable = this.translate.instant('core.unknown');
+            this.maxSubmissionsReadable = this.maxSubmissions < 0 ? undefined : this.translate.instant('core.unknown');
             this.unlimitedFiles = true;
         } else {
             this.maxSubmissionsReadable = String(this.maxSubmissions);
diff --git a/src/components/attachments/core-attachments.html b/src/components/attachments/core-attachments.html
index 7a1abcda8..f57780bad 100644
--- a/src/components/attachments/core-attachments.html
+++ b/src/components/attachments/core-attachments.html
@@ -1,5 +1,6 @@
 <ion-item text-wrap>
-    {{ 'core.maxsizeandattachments' | translate:{$a: {size: maxSizeReadable, attachments: maxSubmissionsReadable} } }}
+    <span *ngIf="maxSubmissionsReadable">{{ 'core.maxsizeandattachments' | translate:{$a: {size: maxSizeReadable, attachments: maxSubmissionsReadable} } }}</span>
+    <span *ngIf="!maxSubmissionsReadable">{{ 'core.maxfilesize' | translate:{$a: maxSizeReadable} }}</span>
     <span [core-mark-required]="required" class="core-mark-required"></span>
 </ion-item>
 <ion-item text-wrap *ngIf="fileTypes && fileTypes.mimetypes && fileTypes.mimetypes.length">
diff --git a/src/lang/en.json b/src/lang/en.json
index c6c46dc48..2a1dc13f5 100644
--- a/src/lang/en.json
+++ b/src/lang/en.json
@@ -143,6 +143,7 @@
     "loadmore": "Load more",
     "location": "Location",
     "lostconnection": "Your authentication token is invalid or has expired. You will have to reconnect to the site.",
+    "maxfilesize": "Maximum size for new files: {{$a}}",
     "maxsizeandattachments": "Maximum file size: {{$a.size}}, maximum number of files: {{$a.attachments}}",
     "min": "min",
     "mins": "mins",
diff --git a/upgrade.txt b/upgrade.txt
index f66263f6a..1f2e73f6f 100644
--- a/upgrade.txt
+++ b/upgrade.txt
@@ -1,6 +1,10 @@
 This files describes API changes in the Moodle Mobile app,
 information provided here is intended especially for developers.
 
+=== 3.9.3 ===
+
+- In the core-attachments component, passing a -1 as maxSize or maxSubmissions used to mean "unknown limit". Now -1 means unlimited.
+
 === 3.8.3 ===
 
 - CoreFileProvider.writeFileDataInFile has been deprecated. Please use CoreFileHelperProvider.writeFileDataInFile instead.