diff --git a/modules/infinite-scroll/infinity.php b/modules/infinite-scroll/infinity.php
index 5bb1572ee5e16..e82c104098246 100644
--- a/modules/infinite-scroll/infinity.php
+++ b/modules/infinite-scroll/infinity.php
@@ -974,7 +974,7 @@ function query() {
 			$results['type'] = 'empty';
 		}
 
-		echo json_encode( apply_filters( 'infinite_scroll_results', $results, $query_args, self::wp_query() ) );
+		echo wp_json_encode( apply_filters( 'infinite_scroll_results', $results, $query_args, self::wp_query() ) );
 		die;
 	}
 
@@ -1191,3 +1191,149 @@ function the_neverending_home_page_theme_support() {
 	// Don't load the admin bar when doing the AJAX response.
 	show_admin_bar( false );
 }
+
+/**
+ * Include the wp_json_encode functions for pre-wordpress-4.1
+ */
+
+if ( ! function_exists( 'wp_json_encode' ) ) :
+	/**
+	 * Encode a variable into JSON, with some sanity checks.
+	 *
+	 * @since 4.1.0
+	 *
+	 * @param mixed $data    Variable (usually an array or object) to encode as JSON.
+	 * @param int   $options Optional. Options to be passed to json_encode(). Default 0.
+	 * @param int   $depth   Optional. Maximum depth to walk through $data. Must be
+	 *                       greater than 0. Default 512.
+	 * @return bool|string The JSON encoded string, or false if it cannot be encoded.
+	 */
+	function wp_json_encode( $data, $options = 0, $depth = 512 ) {
+		/*
+		 * json_encode() has had extra params added over the years.
+		 * $options was added in 5.3, and $depth in 5.5.
+		 * We need to make sure we call it with the correct arguments.
+		 */
+		if ( version_compare( PHP_VERSION, '5.5', '>=' ) ) {
+			$args = array( $data, $options, $depth );
+		} elseif ( version_compare( PHP_VERSION, '5.3', '>=' ) ) {
+			$args = array( $data, $options );
+		} else {
+			$args = array( $data );
+		}
+
+		$json = call_user_func_array( 'json_encode', $args );
+
+		// If json_encode() was successful, no need to do more sanity checking.
+		// ... unless we're in an old version of PHP, and json_encode() returned
+		// a string containing 'null'. Then we need to do more sanity checking.
+		if ( false !== $json && ( version_compare( PHP_VERSION, '5.5', '>=' ) || false === strpos( $json, 'null' ) ) )  {
+			return $json;
+		}
+
+		try {
+			$args[0] = _wp_json_sanity_check( $data, $depth );
+		} catch ( Exception $e ) {
+			return false;
+		}
+
+		return call_user_func_array( 'json_encode', $args );
+	}
+endif;
+
+if ( ! function_exists( '_wp_json_sanity_check' ) ) :
+	/**
+	 * Perform sanity checks on data that shall be encoded to JSON.
+	 *
+	 * @see wp_json_encode()
+	 *
+	 * @since 4.1.0
+	 * @access private
+	 * @internal
+	 *
+	 * @param mixed $data  Variable (usually an array or object) to encode as JSON.
+	 * @param int   $depth Maximum depth to walk through $data. Must be greater than 0.
+	 * @return mixed The sanitized data that shall be encoded to JSON.
+	 */
+	function _wp_json_sanity_check( $data, $depth ) {
+		if ( $depth < 0 ) {
+			throw new Exception( 'Reached depth limit' );
+		}
+
+		if ( is_array( $data ) ) {
+			$output = array();
+			foreach ( $data as $id => $el ) {
+				// Don't forget to sanitize the ID!
+				if ( is_string( $id ) ) {
+					$clean_id = _wp_json_convert_string( $id );
+				} else {
+					$clean_id = $id;
+				}
+
+				// Check the element type, so that we're only recursing if we really have to.
+				if ( is_array( $el ) || is_object( $el ) ) {
+					$output[ $clean_id ] = _wp_json_sanity_check( $el, $depth - 1 );
+				} elseif ( is_string( $el ) ) {
+					$output[ $clean_id ] = _wp_json_convert_string( $el );
+				} else {
+					$output[ $clean_id ] = $el;
+				}
+			}
+		} elseif ( is_object( $data ) ) {
+			$output = new stdClass;
+			foreach ( $data as $id => $el ) {
+				if ( is_string( $id ) ) {
+					$clean_id = _wp_json_convert_string( $id );
+				} else {
+					$clean_id = $id;
+				}
+
+				if ( is_array( $el ) || is_object( $el ) ) {
+					$output->$clean_id = _wp_json_sanity_check( $el, $depth - 1 );
+				} elseif ( is_string( $el ) ) {
+					$output->$clean_id = _wp_json_convert_string( $el );
+				} else {
+					$output->$clean_id = $el;
+				}
+			}
+		} elseif ( is_string( $data ) ) {
+			return _wp_json_convert_string( $data );
+		} else {
+			return $data;
+		}
+
+		return $output;
+	}
+endif;
+
+if ( ! function_exists( '_wp_json_convert_string' ) ) :
+	/**
+	 * Convert a string to UTF-8, so that it can be safely encoded to JSON.
+	 *
+	 * @see _wp_json_sanity_check()
+	 *
+	 * @since 4.1.0
+	 * @access private
+	 * @internal
+	 *
+	 * @param string $string The string which is to be converted.
+	 * @return string The checked string.
+	 */
+	function _wp_json_convert_string( $string ) {
+		static $use_mb = null;
+		if ( is_null( $use_mb ) ) {
+			$use_mb = function_exists( 'mb_convert_encoding' );
+		}
+
+		if ( $use_mb ) {
+			$encoding = mb_detect_encoding( $string, mb_detect_order(), true );
+			if ( $encoding ) {
+				return mb_convert_encoding( $string, 'UTF-8', $encoding );
+			} else {
+				return mb_convert_encoding( $string, 'UTF-8', 'UTF-8' );
+			}
+		} else {
+			return wp_check_invalid_utf8( $string, true );
+		}
+	}
+endif;