diff --git a/config.h b/config.h
index 955e5c5..6752699 100644
--- a/config.h
+++ b/config.h
@@ -63,6 +63,7 @@ static const Rule rules[] = {
     {"jetbrains-pycharm",       NULL,       NULL,                       0,          0,          0,                  0,          1,          1,              -1},
     {"jetbrains-idea",          NULL,       "Welcome to IntelliJ IDEA", 0,          1,          0,                  0,          1,          0,              -1},
     {"firefox",                 NULL,       NULL,                       0,          0,          1,                  0,          0,          0,              -1},
+    {"firefox",                 NULL,       "Picture-in-Picture",       DWM_ALL_TAGS,        1,          0,                  0,          0,          0,              -1},
 };
 
 /* layout(s) */
diff --git a/dwm.c b/dwm.c
index 6c0e6a0..34c3be8 100644
--- a/dwm.c
+++ b/dwm.c
@@ -76,6 +76,8 @@
 #define VERSION_MINOR               0
 #define XEMBED_EMBEDDED_VERSION (VERSION_MAJOR << 16) | VERSION_MINOR
 
+#define DWM_ALL_TAGS				0x1FF
+
 /* enums */
 enum { CurNormal, CurResize, CurMove, CurLast }; /* cursor */
 enum { SchemeNorm, SchemeSel }; /* color schemes */
@@ -552,7 +554,7 @@ buttonpress(XEvent *e)
 	if (ev->window == selmon->barwin) {
 		i = x = 0;
 		for (c = m->clients; c; c = c->next)
-			occ |= c->tags == 255 ? 0 : c->tags;
+			occ |= c->tags == DWM_ALL_TAGS ? 0 : c->tags;
 		do {
 			/* do not reserve space for vacant tags */
 			if (!(occ & 1 << i || m->tagset[m->seltags] & 1 << i))
@@ -907,7 +909,7 @@ drawbar(Monitor *m)
 
 	resizebarwin(m);
 	for (c = m->clients; c; c = c->next) {
-		occ |= c->tags == 255 ? 0 : c->tags;
+		occ |= c->tags == DWM_ALL_TAGS ? 0 : c->tags;
 		if (c->isurgent)
 			urg |= c->tags;
 	}