diff --git a/20181203/hp-20181203.pdf b/20181203/hp-20181203.pdf
index b72be290152b4e33116e29069103ad41556e0c26..12ffbf8e63fc5e85aa4dd6c525b4a9c8836e1856 100644
Binary files a/20181203/hp-20181203.pdf and b/20181203/hp-20181203.pdf differ
diff --git a/20181203/hp-20181203.tex b/20181203/hp-20181203.tex
index 0a3acf1e1b50922248c20c61362e90e1c04db226..3ea9739a0530dc66cead837e7f59294e266904b9 100644
--- a/20181203/hp-20181203.tex
+++ b/20181203/hp-20181203.tex
@@ -457,7 +457,7 @@
     #include <avr/io.h>
     ...
     DDRC = 0xfd;
-    while (PINC & 0x02 == 0)
+    while ((PINC & 0x02) == 0)
       ; /* just wait */
   \end{lstlisting}
   \begin{picture}(0,0)(-1.5,-0.42)