diff --git a/dist/commonmark.js b/dist/commonmark.js
index 0c9cdb5c..9bbaa660 100644
--- a/dist/commonmark.js
+++ b/dist/commonmark.js
@@ -3849,8 +3849,10 @@ var scanDelims = function(cc) {
               !(reWhitespaceChar.test(char_after)) &&
               !(rePunctuation.test(char_after)));
     if (cc === C_UNDERSCORE) {
-        can_open = left_flanking && !right_flanking;
-        can_close = right_flanking && !left_flanking;
+        can_open = left_flanking &&
+            (!right_flanking || rePunctuation.test(char_before));
+        can_close = right_flanking &&
+            (!left_flanking || rePunctuation.test(char_after));
     } else {
         can_open = left_flanking;
         can_close = right_flanking;