diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbb6317..b7ce915 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,9 @@ Fixes:
    Fix handling tab when removing trailing whitespace, especially in connection
    with ATX headers.
 
+ - [#251](https://github.com/mity/md4c/issues/251):
+   Fix handling of allowed non-alphanumeric characters in URL detection.
+
 
 ## Version 0.5.2
 
diff --git a/src/md4c.c b/src/md4c.c
index 91ada64..3e73594 100644
--- a/src/md4c.c
+++ b/src/md4c.c
@@ -3978,9 +3978,9 @@ md_analyze_permissive_autolink(MD_CTX* ctx, int mark_index)
             } else if(end < line_end  &&
                         ISANYOF(end, URL_MAP[i].allowed_nonalnum_chars)  &&
                         md_scan_right_for_resolved_mark(ctx, right_cursor, end, &right_cursor) == NULL  &&
-                        ((end > line_beg && (ISALNUM(end-1)
+                        ((end > line_beg && (ISALNUM(end-1) || ISANYOF(end-1, URL_MAP[i].allowed_nonalnum_chars)
                                              || CH(end-1) == _T(')')))  ||  CH(end) == _T('('))  &&
-                        ((end+1 < line_end && (ISALNUM(end+1)
+                        ((end+1 < line_end && (ISALNUM(end+1) || ISANYOF(end+1, URL_MAP[i].allowed_nonalnum_chars)
                                                || CH(end+1) == _T('(')))  ||  CH(end) == _T(')')))
             {
                 if(CH(end) == URL_MAP[i].delim_char)