diff --git a/src/sigar.c b/src/sigar.c
index 242afb74..1d97a295 100644
--- a/src/sigar.c
+++ b/src/sigar.c
@@ -148,6 +148,11 @@ SIGAR_DECLARE(int) sigar_proc_cpu_get(sigar_t *sigar, sigar_pid_t pid,
 
     memcpy(prev, proccpu, sizeof(*prev));
 
+    if (proccpu->total < otime) {
+        /* XXX this should not happen */
+        otime = 0;
+    }
+
     if (otime == 0) {
         proccpu->percent = 0.0;
         /* first time called */