diff --git a/decoder/ih264d_parse_bslice.c b/decoder/ih264d_parse_bslice.c
index 443dec2..f2a1b01 100644
--- a/decoder/ih264d_parse_bslice.c
+++ b/decoder/ih264d_parse_bslice.c
@@ -1398,7 +1398,8 @@
         {
             u1_max_ref_idx = MAX_FRAMES << 1;
         }
-        if((u4_temp > u1_max_ref_idx) || (ui_temp1 > u1_max_ref_idx))
+        if((u4_temp > u1_max_ref_idx) || (ui_temp1 > u1_max_ref_idx)
+                        || (u4_temp < 1) || (ui_temp1 < 1))
         {
             return ERROR_NUM_REF;
         }
diff --git a/decoder/ih264d_parse_pslice.c b/decoder/ih264d_parse_pslice.c
index db71b6a..c6ce916 100644
--- a/decoder/ih264d_parse_pslice.c
+++ b/decoder/ih264d_parse_pslice.c
@@ -1957,7 +1957,7 @@
 
 
         UWORD8 u1_max_ref_idx = MAX_FRAMES << u1_field_pic_flag;
-        if(u4_temp > u1_max_ref_idx)
+        if(u4_temp > u1_max_ref_idx || u4_temp < 1)
         {
             return ERROR_NUM_REF;
         }