diff --git a/src/html.cc b/src/html.cc
index 23fdd86..c3a214f 100644
--- a/src/html.cc
+++ b/src/html.cc
@@ -2569,7 +2569,7 @@ static const char* Html_get_javascript_link(DilloHtml *html)
 
    if (dStrnAsciiCasecmp("javascript", Buf.c_str(), 10) == 0) {
       i = strcspn(Buf.c_str(), "'\"");
-      ch = Buf.at( i );
+      ch = i == Buf.size() ? '0' : Buf.at( i );
       if ((ch == '"' || ch == '\'') &&
           (p2 = strchr(Buf.data() + i + 1 , ch))) {
          p1 = Buf.data() + i;