diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index bcd56f748d..7d4a51f939 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -1687,17 +1687,19 @@ function path_join( $base, $path ) {
  *
  * On windows systems, replaces backslashes with forward slashes
  * and forces upper-case drive letters.
- * Ensures that no duplicate slashes exist.
+ * Allows for two leading slashes for Windows network shares, but
+ * ensures that all other duplicate slashes are reduced to a single.
  *
  * @since 3.9.0
  * @since 4.4.0 Ensures upper-case drive letters on Windows systems.
+ * @since 4.5.0 Allows for Windows network shares.
  *
  * @param string $path Path to normalize.
  * @return string Normalized path.
  */
 function wp_normalize_path( $path ) {
 	$path = str_replace( '\\', '/', $path );
-	$path = preg_replace( '|/+|','/', $path );
+	$path = preg_replace( '|(?<=.)/+|', '/', $path );
 	if ( ':' === substr( $path, 1, 1 ) ) {
 		$path = ucfirst( $path );
 	}
diff --git a/tests/phpunit/tests/file.php b/tests/phpunit/tests/file.php
index 8ee3e8de20..0ac1484c93 100644
--- a/tests/phpunit/tests/file.php
+++ b/tests/phpunit/tests/file.php
@@ -175,4 +175,26 @@ class Tests_File extends WP_UnitTestCase {
 		);
 	}
 
+	/**
+	 * @dataProvider data_wp_normalize_path
+	 */
+	function test_wp_normalize_path( $path, $expected ) {
+		$this->assertEquals( $expected, wp_normalize_path( $path ) );
+	}
+	function data_wp_normalize_path() {
+		return array(
+			// Windows paths
+			array( 'C:\\www\\path\\', 'C:/www/path/' ),
+			array( 'C:\\www\\\\path\\', 'C:/www/path/' ),
+			array( 'c:/www/path', 'C:/www/path' ),
+			array( 'c:\\www\\path\\', 'C:/www/path/' ), // uppercase drive letter
+			array( '\\\\Domain\\DFSRoots\\share\\path\\', '//Domain/DFSRoots/share/path/' ),
+			array( '\\\\Server\\share\\path', '//Server/share/path' ),
+
+			// Linux paths
+			array( '/www/path/', '/www/path/' ),
+			array( '/www/path/////', '/www/path/' ),
+			array( '/www/path', '/www/path' ),
+		);
+	}
 }