diff --git a/c/src/p2fa.c b/c/src/p2fa.c
index ff09ed0..2fff063 100644
--- a/c/src/p2fa.c
+++ b/c/src/p2fa.c
@@ -110,7 +110,7 @@ int readButtons() {
 int getBtn() {
     while (1) {
         int key = readButtons();
-        if (!isBlocking) {
+        if (isBlocking == 0) {
             return key;
         }
         if (key != -1) {