diff --git a/android/app/src/main/java/com/mattermost/share/RealPathUtil.java b/android/app/src/main/java/com/mattermost/share/RealPathUtil.java
index de20a0897b..adf714a074 100644
--- a/android/app/src/main/java/com/mattermost/share/RealPathUtil.java
+++ b/android/app/src/main/java/com/mattermost/share/RealPathUtil.java
@@ -7,6 +7,7 @@ import android.os.Build;
 import android.provider.DocumentsContract;
 import android.provider.MediaStore;
 import android.content.ContentUris;
+import android.content.ContentResolver;
 import android.os.Environment;
 import android.webkit.MimeTypeMap;
 
@@ -98,6 +99,7 @@ public class RealPathUtil {
                 cacheDir.mkdirs();
             }
 
+            String mimeType = getMimeType(uri.getPath());
             tmpFile = File.createTempFile("tmp", fileName, cacheDir);
 
             ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(uri, "r");
@@ -182,6 +184,11 @@ public class RealPathUtil {
         return getMimeType(file);
     }
 
+    public static String getMimeTypeFromUri(final Context context, final Uri uri) {
+        ContentResolver cR = context.getContentResolver();
+        return cR.getType(uri);
+    }
+
     public static void deleteTempFiles(final File dir) {
         try {
             if (dir.isDirectory()) {
diff --git a/android/app/src/main/java/com/mattermost/share/ShareModule.java b/android/app/src/main/java/com/mattermost/share/ShareModule.java
index de64a6bb1a..6500b660a4 100644
--- a/android/app/src/main/java/com/mattermost/share/ShareModule.java
+++ b/android/app/src/main/java/com/mattermost/share/ShareModule.java
@@ -126,7 +126,7 @@ public class ShareModule extends ReactContextBaseJavaModule {
                     map = Arguments.createMap();
                     text = "file://" + filePath;
                     map.putString("value", text);
-                    map.putString("type", RealPathUtil.getMimeType(filePath));
+                    map.putString("type", RealPathUtil.getMimeTypeFromUri(currentActivity, uri));
                     items.pushMap(map);
                 }
             }
diff --git a/app/utils/file.js b/app/utils/file.js
index 8794d222c8..c68f584ec9 100644
--- a/app/utils/file.js
+++ b/app/utils/file.js
@@ -3,11 +3,13 @@
 
 import {Platform} from 'react-native';
 import RNFetchBlob from 'react-native-fetch-blob';
+import mimeDB from 'mime-db';
 
 import {lookupMimeType} from 'mattermost-redux/utils/file_utils';
 
 import {DeviceTypes} from 'app/constants/';
 
+const EXTRACT_TYPE_REGEXP = /^\s*([^;\s]*)(?:;|\s|$)/;
 const {DOCUMENTS_PATH, IMAGES_PATH, VIDEOS_PATH} = DeviceTypes;
 const DEFAULT_SERVER_MAX_FILE_SIZE = 50 * 1024 * 1024;// 50 Mb
 
@@ -32,6 +34,9 @@ const SUPPORTED_VIDEO_FORMAT = Platform.select({
     android: ['video/3gpp', 'video/x-matroska', 'video/mp4', 'video/webm'],
 });
 
+const types = {};
+const extensions = {};
+
 export function generateId() {
     // Implementation taken from http://stackoverflow.com/a/2117523
     let id = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
@@ -144,3 +149,69 @@ export const isVideo = (file) => {
 
     return SUPPORTED_VIDEO_FORMAT.includes(mime);
 };
+
+/**
+ * Get the default extension for a MIME type.
+ *
+ * @param {string} type
+ * @return {boolean|string}
+ */
+
+export function getExtensionFromMime(type) {
+    if (!Object.keys(extensions).length) {
+        populateMaps();
+    }
+
+    if (!type || typeof type !== 'string') {
+        return false;
+    }
+
+    // TODO: use media-typer
+    const match = EXTRACT_TYPE_REGEXP.exec(type);
+
+    // get extensions
+    const exts = match && extensions[match[1].toLowerCase()];
+
+    if (!exts || !exts.length) {
+        return false;
+    }
+
+    return exts[0];
+}
+
+/**
+ * Populate the extensions and types maps.
+ * @private
+ */
+
+function populateMaps() {
+    // source preference (least -> most)
+    const preference = ['nginx', 'apache', undefined, 'iana']; //eslint-disable-line no-undefined
+
+    Object.keys(mimeDB).forEach((type) => {
+        const mime = mimeDB[type];
+        const exts = mime.extensions;
+
+        if (!exts || !exts.length) {
+            return;
+        }
+
+        extensions[type] = exts;
+
+        for (let i = 0; i < exts.length; i++) {
+            const extension = exts[i];
+
+            if (types[extension]) {
+                const from = preference.indexOf(mimeDB[types[extension]].source);
+                const to = preference.indexOf(mime.source);
+
+                if (types[extension] !== 'application/octet-stream' &&
+                    (from > to || (from === to && types[extension].substr(0, 12) === 'application/'))) {
+                    continue;
+                }
+            }
+
+            types[extension] = type;
+        }
+    });
+}
diff --git a/share_extension/android/extension_post/extension_post.js b/share_extension/android/extension_post/extension_post.js
index a2f92368b2..9a5f1fbb40 100644
--- a/share_extension/android/extension_post/extension_post.js
+++ b/share_extension/android/extension_post/extension_post.js
@@ -6,6 +6,7 @@ import {NavigationActions} from 'react-navigation';
 import TouchableItem from 'react-navigation/src/views/TouchableItem';
 import PropTypes from 'prop-types';
 import {intlShape} from 'react-intl';
+
 import {
     Image,
     NativeModules,
@@ -25,6 +26,7 @@ import {getFormattedFileSize, lookupMimeType} from 'mattermost-redux/utils/file_
 
 import PaperPlane from 'app/components/paper_plane';
 import mattermostManaged from 'app/mattermost_managed';
+import {getExtensionFromMime} from 'app/utils/file';
 import {emptyFunction} from 'app/utils/general';
 import {preventDoubleTap} from 'app/utils/tap';
 import {changeOpacity, makeStyleSheetFromTheme} from 'app/utils/theme';
@@ -278,15 +280,20 @@ export default class ExtensionPost extends PureComponent {
                     break;
                 default: {
                     const fullPath = item.value;
-                    const filename = fullPath.replace(/^.*[\\/]/, '');
-                    const extension = filename.split('.').pop();
                     const fileSize = await RNFetchBlob.fs.stat(fullPath);
+                    let filename = fullPath.replace(/^.*[\\/]/, '');
+                    let extension = filename.split('.').pop();
+                    if (extension === filename) {
+                        extension = getExtensionFromMime(item.type);
+                        filename = `${filename}.${extension}`;
+                    }
+
                     totalSize += fileSize.size;
                     files.push({
                         extension,
                         filename,
                         fullPath,
-                        mimeType: lookupMimeType(filename.toLowerCase()),
+                        mimeType: item.type || lookupMimeType(filename.toLowerCase()),
                         size: getFormattedFileSize(fileSize),
                         type: item.type,
                     });