diff --git a/libraries/core/src/main/kotlin/io/element/android/libraries/core/mimetype/MimeTypes.kt b/libraries/core/src/main/kotlin/io/element/android/libraries/core/mimetype/MimeTypes.kt
index dee840ea48..3901a32059 100644
--- a/libraries/core/src/main/kotlin/io/element/android/libraries/core/mimetype/MimeTypes.kt
+++ b/libraries/core/src/main/kotlin/io/element/android/libraries/core/mimetype/MimeTypes.kt
@@ -68,7 +68,7 @@ object MimeTypes {
      * A mime type with a wildcard subtype is a filter, not a media type, so replace it with a
      * concrete default for its top level type.
      */
-    fun String?.withDefaultSubtype(): String = when {
+    fun String?.ensureDefaultSubtype(): String = when {
         this == null -> OctetStream
         hasSubtype(this) -> this
         this == Images -> Jpeg
diff --git a/libraries/core/src/test/kotlin/io/element/android/libraries/core/mimetype/MimeTypesTest.kt b/libraries/core/src/test/kotlin/io/element/android/libraries/core/mimetype/MimeTypesTest.kt
index 7ba68fa9b1..f12b73b40b 100644
--- a/libraries/core/src/test/kotlin/io/element/android/libraries/core/mimetype/MimeTypesTest.kt
+++ b/libraries/core/src/test/kotlin/io/element/android/libraries/core/mimetype/MimeTypesTest.kt
@@ -8,28 +8,28 @@
 package io.element.android.libraries.core.mimetype
 
 import com.google.common.truth.Truth.assertThat
-import io.element.android.libraries.core.mimetype.MimeTypes.withDefaultSubtype
+import io.element.android.libraries.core.mimetype.MimeTypes.ensureDefaultSubtype
 import org.junit.Test
 
 class MimeTypesTest {
     @Test
-    fun `withDefaultSubtype keeps a mime type that already has a subtype`() {
-        assertThat(MimeTypes.Png.withDefaultSubtype()).isEqualTo(MimeTypes.Png)
-        assertThat(MimeTypes.Mp4.withDefaultSubtype()).isEqualTo(MimeTypes.Mp4)
-        assertThat(MimeTypes.Pdf.withDefaultSubtype()).isEqualTo(MimeTypes.Pdf)
+    fun `ensureDefaultSubtype keeps a mime type that already has a subtype`() {
+        assertThat(MimeTypes.Png.ensureDefaultSubtype()).isEqualTo(MimeTypes.Png)
+        assertThat(MimeTypes.Mp4.ensureDefaultSubtype()).isEqualTo(MimeTypes.Mp4)
+        assertThat(MimeTypes.Pdf.ensureDefaultSubtype()).isEqualTo(MimeTypes.Pdf)
     }
 
     @Test
-    fun `withDefaultSubtype replaces a wildcard subtype with a concrete one`() {
-        assertThat(MimeTypes.Images.withDefaultSubtype()).isEqualTo(MimeTypes.Jpeg)
-        assertThat(MimeTypes.Videos.withDefaultSubtype()).isEqualTo(MimeTypes.Mp4)
-        assertThat(MimeTypes.Audio.withDefaultSubtype()).isEqualTo(MimeTypes.Mp3)
+    fun `ensureDefaultSubtype replaces a wildcard subtype with a concrete one`() {
+        assertThat(MimeTypes.Images.ensureDefaultSubtype()).isEqualTo(MimeTypes.Jpeg)
+        assertThat(MimeTypes.Videos.ensureDefaultSubtype()).isEqualTo(MimeTypes.Mp4)
+        assertThat(MimeTypes.Audio.ensureDefaultSubtype()).isEqualTo(MimeTypes.Mp3)
     }
 
     @Test
-    fun `withDefaultSubtype falls back to octet stream`() {
-        assertThat(MimeTypes.Any.withDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
-        assertThat("text/*".withDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
-        assertThat(null.withDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
+    fun `ensureDefaultSubtype falls back to octet stream`() {
+        assertThat(MimeTypes.Any.ensureDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
+        assertThat("text/*".ensureDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
+        assertThat(null.ensureDefaultSubtype()).isEqualTo(MimeTypes.OctetStream)
     }
 }
diff --git a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/media/RustMediaLoader.kt b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/media/RustMediaLoader.kt
index 3231c29403..7b3a1d9f10 100644
--- a/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/media/RustMediaLoader.kt
+++ b/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/media/RustMediaLoader.kt
@@ -11,7 +11,7 @@ package io.element.android.libraries.matrix.impl.media
 import io.element.android.libraries.core.coroutine.CoroutineDispatchers
 import io.element.android.libraries.core.extensions.mapFailure
 import io.element.android.libraries.core.extensions.runCatchingExceptions
-import io.element.android.libraries.core.mimetype.MimeTypes.withDefaultSubtype
+import io.element.android.libraries.core.mimetype.MimeTypes.ensureDefaultSubtype
 import io.element.android.libraries.matrix.api.media.MatrixMediaLoader
 import io.element.android.libraries.matrix.api.media.MediaFile
 import io.element.android.libraries.matrix.api.media.MediaSource
@@ -72,7 +72,7 @@ class RustMediaLoader(
                         mediaSource = mediaSource,
                         filename = filename,
                         // Fallback to a default mime type based on the main type, so that the SDK can create a file with the correct extension.
-                        mimeType = mimeType.withDefaultSubtype(),
+                        mimeType = mimeType.ensureDefaultSubtype(),
                         useCache = useCache,
                         tempDir = cacheDirectory.path,
                     )
diff --git a/libraries/mediaupload/impl/src/main/kotlin/io/element/android/libraries/mediaupload/impl/AndroidMediaPreProcessor.kt b/libraries/mediaupload/impl/src/main/kotlin/io/element/android/libraries/mediaupload/impl/AndroidMediaPreProcessor.kt
index 4ef8a2410c..d35fdb6189 100644
--- a/libraries/mediaupload/impl/src/main/kotlin/io/element/android/libraries/mediaupload/impl/AndroidMediaPreProcessor.kt
+++ b/libraries/mediaupload/impl/src/main/kotlin/io/element/android/libraries/mediaupload/impl/AndroidMediaPreProcessor.kt
@@ -26,10 +26,10 @@ import io.element.android.libraries.core.data.tryOrNull
 import io.element.android.libraries.core.extensions.mapFailure
 import io.element.android.libraries.core.extensions.runCatchingExceptions
 import io.element.android.libraries.core.mimetype.MimeTypes
+import io.element.android.libraries.core.mimetype.MimeTypes.ensureDefaultSubtype
 import io.element.android.libraries.core.mimetype.MimeTypes.isMimeTypeAudio
 import io.element.android.libraries.core.mimetype.MimeTypes.isMimeTypeImage
 import io.element.android.libraries.core.mimetype.MimeTypes.isMimeTypeVideo
-import io.element.android.libraries.core.mimetype.MimeTypes.withDefaultSubtype
 import io.element.android.libraries.di.annotations.ApplicationContext
 import io.element.android.libraries.matrix.api.media.AudioInfo
 import io.element.android.libraries.matrix.api.media.FileInfo
@@ -83,7 +83,7 @@ class AndroidMediaPreProcessor(
         mediaOptimizationConfig: MediaOptimizationConfig,
     ): Result<MediaUploadInfo> = withContext(coroutineDispatchers.computation) {
         runCatchingExceptions {
-            val resolvedMimeType = mimeType.withDefaultSubtype()
+            val resolvedMimeType = mimeType.ensureDefaultSubtype()
             val result = when {
                 resolvedMimeType == MimeTypes.Svg -> processSvgImage(uri, resolvedMimeType)
                 resolvedMimeType.isMimeTypeImage() -> {