diff --git a/example4.c b/example4.c
index a24680ee31f3e63e03db2a594f56b992d0c57e50..1dc9ebe4ac56437b34807fb7a210d81b8591a062 100644
--- a/example4.c
+++ b/example4.c
@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <alloca.h>
 #include <signal.h>
 #include <alsa/asoundlib.h>
 
@@ -72,7 +73,7 @@ 	signal(SIGTERM, sighandler);
 
 	// Reading MIDI device.
 	struct pollfd *pfds;
-	int npfds;
+	size_t npfds;
 
 	npfds = snd_seq_poll_descriptors_count(seq_handle, POLLIN);
 	pfds = alloca(sizeof(*pfds) * npfds);