diff --git a/db.c b/db.c
index ce3a590..3626d60 100644
--- a/db.c
+++ b/db.c
@@ -630,7 +630,7 @@ PrepareResult prepare_insert(InputBuffer* input_buffer, Statement* statement) {
   }
 
   int id = atoi(id_string);
-  if (id < 0) {
+  if (id <= 0) {
     return PREPARE_NEGATIVE_ID;
   }
   if (strlen(username) > COLUMN_USERNAME_SIZE) {
@@ -1024,7 +1024,7 @@ int main(int argc, char* argv[]) {
       case (PREPARE_SUCCESS):
         break;
       case (PREPARE_NEGATIVE_ID):
-        printf("ID must be positive.\n");
+        printf("ID must be a positive integer.\n");
         continue;
       case (PREPARE_STRING_TOO_LONG):
         printf("String is too long.\n");