protected function merge_hyphenation_exceptions() {
		$exceptions = [];

		// Merge custom and language specific word hyphenations.
		if ( ! empty( $this->pattern_exceptions ) && ! empty( $this->custom_exceptions ) ) {
			$exceptions = array_merge( $this->custom_exceptions, $this->pattern_exceptions );
		} elseif ( ! empty( $this->pattern_exceptions ) ) {
			$exceptions = $this->pattern_exceptions;
		} elseif ( ! empty( $this->custom_exceptions ) ) {
			$exceptions = $this->custom_exceptions;
		}

		// Update patterns as well.
		$exception_patterns = [];
		foreach ( $exceptions as $exception_key => $exception ) {
			$exception_patterns[ $exception_key ] = self::convert_hyphenation_exception_to_pattern( $exception );
		}

		$this->merged_exception_patterns = $exception_patterns;
	}