diff --git a/src/wp-admin/includes/image.php b/src/wp-admin/includes/image.php
index 0f03e2ca42..573f107605 100644
--- a/src/wp-admin/includes/image.php
+++ b/src/wp-admin/includes/image.php
@@ -556,6 +556,11 @@ function file_is_valid_image( $path ) {
 function file_is_displayable_image( $path ) {
 	$displayable_image_types = array( IMAGETYPE_GIF, IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_BMP );
 
+	// IMAGETYPE_ICO is only defined in PHP 5.3+.
+	if ( defined( 'IMAGETYPE_ICO' ) ) {
+		$displayable_image_types[] = IMAGETYPE_ICO;
+	}
+
 	$info = @getimagesize( $path );
 	if ( empty( $info ) ) {
 		$result = false;
diff --git a/tests/phpunit/data/images/test-image.ico b/tests/phpunit/data/images/test-image.ico
new file mode 100644
index 0000000000..2145492a2b
Binary files /dev/null and b/tests/phpunit/data/images/test-image.ico differ
diff --git a/tests/phpunit/tests/image/functions.php b/tests/phpunit/tests/image/functions.php
index f36fe6fdc6..915b695b42 100644
--- a/tests/phpunit/tests/image/functions.php
+++ b/tests/phpunit/tests/image/functions.php
@@ -61,6 +61,11 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 			'test-image.jpg',
 		);
 
+		// IMAGETYPE_ICO is only defined in PHP 5.3+.
+		if ( defined( 'IMAGETYPE_ICO' ) ) {
+			$files[] = 'test-image.ico';
+		}
+
 		foreach ( $files as $file ) {
 			$this->assertTrue( file_is_valid_image( DIR_TESTDATA . '/images/' . $file ), "file_is_valid_image($file) should return true" );
 		}
@@ -87,6 +92,11 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 			'test-image.jpg',
 		);
 
+		// IMAGETYPE_ICO is only defined in PHP 5.3+.
+		if ( defined( 'IMAGETYPE_ICO' ) ) {
+			$files[] = 'test-image.ico';
+		}
+
 		foreach ( $files as $file ) {
 			$this->assertTrue( file_is_displayable_image( DIR_TESTDATA . '/images/' . $file ), "file_is_valid_image($file) should return true" );
 		}