diff --git a/backend/gs1.c b/backend/gs1.c
index d1de74bf..203fc787 100644
--- a/backend/gs1.c
+++ b/backend/gs1.c
@@ -449,7 +449,7 @@ int gs1_verify(struct zint_symbol *symbol, const unsigned char source[], const s
         }
         
         if (ai_value[i] == 253) { // GDTI
-            if ((data_length[i] < 14) || (data_length[i] > 31)) {
+            if ((data_length[i] < 14) || (data_length[i] > 30)) {
                 error_latch = 1;
             } else {
                 error_latch = 0;