diff --git a/crypto/bn/bn_print.c b/crypto/bn/bn_print.c
index 8d06405ab687caa71f3b537f1ff9e7f58cef9a13..78589dba5bdb3549f92290ee3004774e6dc3fba2 100644
--- a/crypto/bn/bn_print.c
+++ b/crypto/bn/bn_print.c
@@ -139,7 +139,7 @@ int BN_hex2bn(BIGNUM **bn, const char *a)
     for (i = 0; i <= (INT_MAX/4) && isxdigit((unsigned char)a[i]); i++)
         continue;
 
-    if (i > INT_MAX/4)
+    if (i == 0 || i > INT_MAX/4)
         goto err;
 
     num = i + neg;
@@ -209,7 +209,7 @@ int BN_dec2bn(BIGNUM **bn, const char *a)
     for (i = 0; i <= (INT_MAX/4) && isdigit((unsigned char)a[i]); i++)
         continue;
 
-    if (i > INT_MAX/4)
+    if (i == 0 || i > INT_MAX/4)
         goto err;
 
     num = i + neg;