diff --git a/src/document.c b/src/document.c
index ab825b87..c94a3477 100644
--- a/src/document.c
+++ b/src/document.c
@@ -2751,7 +2751,7 @@ hoedown_document_new(
 
 	memset(doc->active_char, 0x0, 256);
 
-	if (doc->md.emphasis || doc->md.double_emphasis || doc->md.triple_emphasis) {
+	if (doc->md.emphasis || doc->md.double_emphasis || doc->md.triple_emphasis || doc->md.underline) {
 		doc->active_char['*'] = MD_CHAR_EMPHASIS;
 		doc->active_char['_'] = MD_CHAR_EMPHASIS;
 		if (extensions & HOEDOWN_EXT_STRIKETHROUGH)
diff --git a/test/Tests/Underline.html b/test/Tests/Underline.html
new file mode 100644
index 00000000..c2a8bbad
--- /dev/null
+++ b/test/Tests/Underline.html
@@ -0,0 +1 @@
+<p>This <u>underline</u> will work.</p>
diff --git a/test/Tests/Underline.text b/test/Tests/Underline.text
new file mode 100644
index 00000000..8068546c
--- /dev/null
+++ b/test/Tests/Underline.text
@@ -0,0 +1 @@
+This _underline_ will work.
diff --git a/test/config.json b/test/config.json
index b6ecb551..d3e170e8 100644
--- a/test/config.json
+++ b/test/config.json
@@ -101,6 +101,11 @@
             "input": "Tests/Math.text",
             "output": "Tests/Math.html",
             "flags": ["--math"]
+        },
+        {
+            "input": "Tests/Underline.text",
+            "output": "Tests/Underline.html",
+            "flags": ["--underline"]
         }
     ]
 }