diff --git a/native/input/input-state-container.react.js b/native/input/input-state-container.react.js
--- a/native/input/input-state-container.react.js
+++ b/native/input/input-state-container.react.js
@@ -1229,17 +1229,29 @@
         path = resolvedPath;
       }
     }
+
+    let uploadOptions = {
+      uploadType: FileSystem.FileSystemUploadType.MULTIPART,
+      fieldName: 'multimedia',
+      headers: {
+        Accept: 'application/json',
+      },
+      parameters,
+    };
+    if (Platform.OS === 'android' && path.endsWith('.dat')) {
+      // expo-file-system is not able to deduce the MIME type of .dat files, so
+      // we specify it explicitly here. Without this, we get this error:
+      //   guessContentTypeFromName(file.name) must not be null
+      uploadOptions = {
+        ...uploadOptions,
+        mimeType: 'application/octet-stream',
+      };
+    }
+
     const uploadTask = FileSystem.createUploadTask(
       url,
       path,
-      {
-        uploadType: FileSystem.FileSystemUploadType.MULTIPART,
-        fieldName: 'multimedia',
-        headers: {
-          Accept: 'application/json',
-        },
-        parameters,
-      },
+      uploadOptions,
       uploadProgress => {
         if (options && options.onProgress) {
           const { totalByteSent, totalBytesExpectedToSend } = uploadProgress;
diff --git a/native/utils/blob-service-upload.js b/native/utils/blob-service-upload.js
--- a/native/utils/blob-service-upload.js
+++ b/native/utils/blob-service-upload.js
@@ -18,6 +18,7 @@
   if (input.blobInput.type !== 'uri') {
     throw new Error('Wrong blob data type');
   }
+
   let path = input.blobInput.uri;
   if (Platform.OS === 'android') {
     const resolvedPath = pathFromURI(path);
@@ -25,17 +26,29 @@
       path = resolvedPath;
     }
   }
+
   const headers = authMetadata && createDefaultHTTPRequestHeaders(authMetadata);
+  let uploadOptions = {
+    uploadType: FileSystem.FileSystemUploadType.MULTIPART,
+    fieldName: 'blob_data',
+    httpMethod: method,
+    parameters: { blob_hash: input.blobHash },
+    headers,
+  };
+  if (Platform.OS === 'android' && path.endsWith('.dat')) {
+    // expo-file-system is not able to deduce the MIME type of .dat files, so we
+    // specify it explicitly here. Without this, we get this error:
+    //   guessContentTypeFromName(file.name) must not be null
+    uploadOptions = {
+      ...uploadOptions,
+      mimeType: 'application/octet-stream',
+    };
+  }
+
   const uploadTask = FileSystem.createUploadTask(
     url,
     path,
-    {
-      uploadType: FileSystem.FileSystemUploadType.MULTIPART,
-      fieldName: 'blob_data',
-      httpMethod: method,
-      parameters: { blob_hash: input.blobHash },
-      headers,
-    },
+    uploadOptions,
     uploadProgress => {
       if (options?.onProgress) {
         const { totalByteSent, totalBytesExpectedToSend } = uploadProgress;