diff --git a/Source/DelphiZXIngQRCode.pas b/Source/DelphiZXIngQRCode.pas
index 6f54de9..e376c8a 100644
--- a/Source/DelphiZXIngQRCode.pas
+++ b/Source/DelphiZXIngQRCode.pas
@@ -1048,7 +1048,7 @@ function TEncoder.FilterContent(const Content: WideString; Mode: TMode;
     end else
     if (Mode = qmAlphanumeric) then
     begin
-      CanAdd := GetAlphanumericCode(Ord(Content[X])) > 0;
+      CanAdd := GetAlphanumericCode(Ord(Content[X])) > -1;
     end else
     if (Mode = qmByte) then
     begin