diff --git a/du3/program.c b/du3/program.c
index d43389e..b2454dc 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -131,7 +131,7 @@ int main()
             //** konecna faza = vypisovanie vysledkov
 
             //ak systematicka chyba
-            if (isLineInvalid = true || op == 'N' || IsArithCorrect(strtof(num1Temp, strtofEndPtr),strtof(num2Temp, strtofEndPtr), op1) == -1)
+            if (isLineInvalid = true || op1 == 'N' || IsArithCorrect(strtof(num1Temp, strtofEndPtr),strtof(num2Temp, strtofEndPtr), op1) == -1)
             {
                 printf("CHYBA\n");
             }