diff --git a/include/sigar_private.h b/include/sigar_private.h
index 78f75758..81a03a3f 100644
--- a/include/sigar_private.h
+++ b/include/sigar_private.h
@@ -114,7 +114,7 @@
     ((sigar_uint64_t)(s) * (sigar_uint64_t)SIGAR_NSEC)
 
 /* cpu ticks to milliseconds */
-#define SIGAR_TICK2MSEC(s) ((s) * (SIGAR_MSEC / sigar->ticks))
+#define SIGAR_TICK2MSEC(s) ((sigar_uint64_t)(s) * ((sigar_uint64_t)SIGAR_MSEC / sigar->ticks))
 #define SIGAR_TICK2NSEC(s) ((sigar_uint64_t)(s) * ((sigar_uint64_t)SIGAR_NSEC / sigar->ticks))
 
 #define IFTYPE_LO  2
diff --git a/src/os/darwin/darwin_sigar.c b/src/os/darwin/darwin_sigar.c
index 6bd32e60..c10b2781 100644
--- a/src/os/darwin/darwin_sigar.c
+++ b/src/os/darwin/darwin_sigar.c
@@ -499,7 +499,7 @@ int sigar_cpu_get(sigar_t *sigar, sigar_cpu_t *cpu)
 
 #else
     int status;
-    long cp_time[CPUSTATES];
+    unsigned long cp_time[CPUSTATES];
     size_t size = sizeof(cp_time);
 
     /* try sysctl first, does not require /dev/kmem perms */