diff --git a/src/unix/linux-core.c b/src/unix/linux-core.c
index 3d2d4cf7..c356e96d 100644
--- a/src/unix/linux-core.c
+++ b/src/unix/linux-core.c
@@ -636,7 +636,7 @@ int uv_uptime(double* uptime) {
   /* Try /proc/uptime first, then fallback to clock_gettime(). */
   
   if (0 == uv__slurp("/proc/uptime", buf, sizeof(buf)))
-    if (1 == sscanf(buf, "%f", uptime))
+    if (1 == sscanf(buf, "%lf", uptime))
       return 0;
 
   /* Try CLOCK_BOOTTIME first, fall back to CLOCK_MONOTONIC if not available