diff --git a/library/src/main/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperation.kt b/library/src/main/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperation.kt
index 34744a7447..ac9eba4938 100644
--- a/library/src/main/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperation.kt
+++ b/library/src/main/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperation.kt
@@ -327,7 +327,7 @@ class ChunkedFileUploadRemoteOperation
                     return if (onWifiConnection) DEFAULT_CHUNK_SIZE else MIN_CHUNK_SIZE
                 }
 
-                return serverMaxChunkSize
+                return serverMaxChunkSize.coerceAtLeast(MIN_CHUNK_SIZE)
             }
 
             private const val ASSEMBLED_FILE_SUFFIX = "/.file"
diff --git a/library/src/test/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperationTest.kt b/library/src/test/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperationTest.kt
index 4ce08c368b..6336f2677e 100644
--- a/library/src/test/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperationTest.kt
+++ b/library/src/test/java/com/owncloud/android/lib/resources/files/ChunkedFileUploadRemoteOperationTest.kt
@@ -89,6 +89,26 @@ class ChunkedFileUploadRemoteOperationTest {
         assertEquals(chunk1.hashCode(), chunk2.hashCode())
     }
 
+    @Test
+    fun testChunkSize() {
+        val min = ChunkedFileUploadRemoteOperation.MIN_CHUNK_SIZE
+        val default = ChunkedFileUploadRemoteOperation.DEFAULT_CHUNK_SIZE
+        val unknown = ChunkedFileUploadRemoteOperation.SERVER_MAX_CHUNK_SIZE_UNKNOWN
+
+        // unknown server value falls back to defaults
+        assertEquals(default, ChunkedFileUploadRemoteOperation.chunkSize(true, unknown))
+        assertEquals(min, ChunkedFileUploadRemoteOperation.chunkSize(false, unknown))
+        assertEquals(default, ChunkedFileUploadRemoteOperation.chunkSize(true, 0))
+
+        // misconfigured tiny server value is clamped to the minimum
+        assertEquals(min, ChunkedFileUploadRemoteOperation.chunkSize(true, 10))
+        assertEquals(min, ChunkedFileUploadRemoteOperation.chunkSize(false, min - 1))
+
+        // sane server values are used as-is
+        assertEquals(min, ChunkedFileUploadRemoteOperation.chunkSize(true, min))
+        assertEquals(100 * MB, ChunkedFileUploadRemoteOperation.chunkSize(false, 100 * MB))
+    }
+
     @Test
     fun testChunking() {
         listOf(1 * MB, 10 * MB, 100 * MB, 1 * GB).forEach { length ->