diff --git a/R/util.R b/R/util.R
index 70ee7ac..7f54e2a 100644
--- a/R/util.R
+++ b/R/util.R
@@ -60,6 +60,7 @@
   x <- gsub("\\{", "\\\\{", x)
   x <- gsub("\\}", "\\\\}", x)
   x <- gsub("\\*", "\\\\*", x)
+  x <- gsub("\\+", "\\\\+", x)
   return(x)
 }