diff --git a/src/main.c b/src/main.c
index 8c0e93d..8f0fd23 100644
--- a/src/main.c
+++ b/src/main.c
@@ -326,8 +326,8 @@ get_section(MD_ATTRIBUTE *attr)
     MD_SIZE l = attr->substr_offsets[1] - attr->substr_offsets[0];
 
     if (attr->substr_types[0] != MD_TEXT_NORMAL || l != 1
-            || !(*s >= '1' && *s <= '8'))
-        return 0;
+            || !(*s >= '0' && *s <= '8'))
+        return -1;
 
     return *s - '0';
 }
@@ -912,7 +912,7 @@ enter_span(MD_SPANTYPE type, void *details, void *ctx_)
             {
                 MD_SPAN_A_DETAIL *d = details;
 
-                if (get_section(&d->href)) {
+                if (get_section(&d->href) >= 0) {
                     BUFFERING_ON();
                     ctx->doc.flags |= DOC_BUFFERED_A;
                 } else if (!d->href.size) {
@@ -1022,7 +1022,7 @@ leave_span(MD_SPANTYPE type, void *details, void *ctx_)
                     BUFFERING_OFF(s, l);
                     ctx->doc.flags &= ~DOC_BUFFERED_A;
 
-                    if (!section)
+                    if (section < 0)
                         return ERR_PARSER_LEAVE_SPAN;
 
                     char buf[UINT32_FMT + 2];