diff --git a/sundown-c/autolink.c b/sundown-c/autolink.c
--- a/sundown-c/autolink.c
+++ b/sundown-c/autolink.c
@@ -235,7 +235,8 @@
 			break;
 	}
 
-	if (link_end < 2 || nb != 1 || np == 0)
+	if (link_end < 2 || nb != 1 || np == 0 ||
+		!isalpha(data[link_end - 1]))
 		return 0;
 
 	link_end = autolink_delim(data, link_end, max_rewind, size);
diff --git a/sundown.cabal b/sundown.cabal
--- a/sundown.cabal
+++ b/sundown.cabal
@@ -1,6 +1,6 @@
 Cabal-version:      >= 1.6
 Name:               sundown
-Version:            0.5.0.1
+Version:            0.5.0.2
 Author:             Francesco Mazzoli (f@mazzo.li)
 Maintainer:         Francesco Mazzoli (f@mazzo.li)
 Build-Type:         Simple