diff --git a/MoveTask.cpp b/MoveTask.cpp
index 38cca04..ea64a1c 100644
--- a/MoveTask.cpp
+++ b/MoveTask.cpp
@@ -128,6 +128,12 @@ static status_t execCp(const std::string& fromPath, const std::string& toPath,
     uint64_t expectedBytes = GetTreeBytes(fromPath);
     uint64_t startFreeBytes = GetFreeBytes(toPath);
 
+    if (expectedBytes > startFreeBytes) {
+        LOG(ERROR) << "Data size " << expectedBytes << " is too large to fit in free space "
+                << startFreeBytes;
+        return -1;
+    }
+
     std::vector<std::string> cmd;
     cmd.push_back(kCpPath);
     cmd.push_back("-p"); /* preserve timestamps, ownership, and permissions */
diff --git a/Utils.cpp b/Utils.cpp
index 72d3801..443df1d 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -432,7 +432,7 @@ status_t NormalizeHex(const std::string& in, std::string& out) {
 uint64_t GetFreeBytes(const std::string& path) {
     struct statvfs sb;
     if (statvfs(path.c_str(), &sb) == 0) {
-        return (uint64_t)sb.f_bfree * sb.f_bsize;
+        return (uint64_t) sb.f_bavail * sb.f_frsize;
     } else {
         return -1;
     }