diff --git a/pidof.c b/pidof.c
index c65aaadb..c4288115 100644
--- a/pidof.c
+++ b/pidof.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <getopt.h>
+#include <limits.h>
 #include <sys/types.h>
 
 #include "c.h"
@@ -30,7 +31,12 @@
 #include <proc/procps.h>
 
 
-#define grow_size(x)	(x = x * 5 / 4 + 1024)
+#define grow_size(x) do { \
+	if ((x) < 0 || (size_t)(x) >= INT_MAX / 5 / sizeof(struct el)) \
+		xerrx(EXIT_FAILURE, _("integer overflow")); \
+	(x) = (x) * 5 / 4 + 1024; \
+} while (0)
+
 #define safe_free(x)	if (x) { free(x); x=NULL; }