diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index 7398d57249..512d17e67b 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -3728,7 +3728,7 @@ function wp_trim_excerpt( $text = '', $post = null ) {
 		 *
 		 * @param int $number The maximum number of words. Default 55.
 		 */
-		$excerpt_length = apply_filters( 'excerpt_length', $excerpt_length );
+		$excerpt_length = (int) apply_filters( 'excerpt_length', $excerpt_length );
 
 		/**
 		 * Filters the string in the "more" link displayed after a trimmed excerpt.
@@ -3773,6 +3773,7 @@ function wp_trim_words( $text, $num_words = 55, $more = null ) {
 
 	$original_text = $text;
 	$text          = wp_strip_all_tags( $text );
+	$num_words     = (int) $num_words;
 
 	/*
 	 * translators: If your word count is based on single characters (e.g. East Asian characters),
diff --git a/tests/phpunit/tests/formatting/WPTrimWords.php b/tests/phpunit/tests/formatting/WPTrimWords.php
index fab62372f7..7b7438de46 100644
--- a/tests/phpunit/tests/formatting/WPTrimWords.php
+++ b/tests/phpunit/tests/formatting/WPTrimWords.php
@@ -73,4 +73,14 @@ class Tests_Formatting_WPTrimWords extends WP_UnitTestCase {
 		restore_previous_locale();
 		$this->assertEquals( $expected, $actual );
 	}
+
+	/**
+	 * @ticket 47867
+	 */
+	function test_works_with_non_numeric_num_words() {
+		$this->assertEquals( '', wp_trim_words( $this->long_text, '', '' ) );
+		$this->assertEquals( '', wp_trim_words( $this->long_text, 'abc', '' ) );
+		$this->assertEquals( '', wp_trim_words( $this->long_text, null, '' ) );
+		$this->assertEquals( 'Lorem ipsum dolor', wp_trim_words( $this->long_text, '3', '' ) );
+	}
 }