diff --git a/src/qrprinter.fnl b/src/qrprinter.fnl
index 56f3713..791de66 100644
--- a/src/qrprinter.fnl
+++ b/src/qrprinter.fnl
@@ -81,7 +81,9 @@ Black modules will be printed as `black_cell`, and white modules will be printed
 (fn encode_string [string]
   "Encode string `string` into a table representing a QR code.
 Returns a 2D sequential table of true/false values representing black/white QR modules."
-  (qrencode.encode_string_8_bit string))
+  (if (~= (string.len string) 0)
+      (qrencode.encode_string_8_bit string)
+      nil))
 
 (fn print_qr_ascii [qr options]
   "Print QR code `qr` to stdout using ASCII characters."