x.c | 3 +++

diff --git a/x.c b/x.c
index 12bc86b81cb03c663381965eddb664b3015884e6..c343ba2bdaf446aba578a55cb219afb73cf00fda 100644
--- a/x.c
+++ b/x.c
@@ -618,6 +618,9 @@
 void
 setsel(char *str, Time t)
 {
+	if (!str)
+		return;
+
 	free(xsel.primary);
 	xsel.primary = str;