diff --git a/third_party/libopenjpeg20/j2k.c b/third_party/libopenjpeg20/j2k.c
index cea614709..afcd597ee 100644
--- a/third_party/libopenjpeg20/j2k.c
+++ b/third_party/libopenjpeg20/j2k.c
@@ -4085,7 +4085,12 @@ static OPJ_BOOL opj_j2k_merge_ppt(opj_tcp_t *p_tcp, opj_event_mgr_t * p_manager)
     /* preconditions */
     assert(p_tcp != 00);
     assert(p_manager != 00);
-    assert(p_tcp->ppt_buffer == NULL);
+
+    if (p_tcp->ppt_buffer != NULL) {
+        opj_event_msg(p_manager, EVT_ERROR,
+                      "opj_j2k_merge_ppt() has already been called\n");
+        return OPJ_FALSE;
+    }
 
     if (p_tcp->ppt == 0U) {
         return OPJ_TRUE;
@@ -8836,7 +8841,10 @@ OPJ_BOOL opj_j2k_read_tile_header(opj_j2k_t * p_j2k,
 
     /* Current marker is the EOC marker ?*/
     if (l_current_marker == J2K_MS_EOC) {
-        p_j2k->m_specific_param.m_decoder.m_state = J2K_STATE_EOC;
+        if (p_j2k->m_specific_param.m_decoder.m_state != J2K_STATE_EOC) {
+            p_j2k->m_current_tile_number = 0;
+            p_j2k->m_specific_param.m_decoder.m_state = J2K_STATE_EOC;
+        }
     }
 
     /* FIXME DOC ???*/