diff --git a/src/XrdFileCache/XrdFileCacheIOEntireFile.cc b/src/XrdFileCache/XrdFileCacheIOEntireFile.cc
index 68144bcfb0d..09ff327a14f 100644
--- a/src/XrdFileCache/XrdFileCacheIOEntireFile.cc
+++ b/src/XrdFileCache/XrdFileCacheIOEntireFile.cc
@@ -64,7 +64,6 @@ void IOEntireFile::StartPrefetch()
 {
    pthread_t tid;
    XrdSysThread::Run(&tid, PrefetchRunner, (void *)(m_prefetch), 0, "XrdFileCache Prefetcher");
-
 }
 
 
@@ -87,8 +86,13 @@ int IOEntireFile::Read (char *buff, long long off, int size)
    clLog()->Debug(XrdCl::AppMsg, "IO::Read() [%p]  %lld@%d %s", this, off, size, m_io.Path());
 
    // protect from reads over the file size
+   if (off >= m_io.FSize() || off < 0)
+   {
+      errno = EINVAL;
+      return -1;
+   }
    if (off + size > m_io.FSize())
-       size =  m_io.FSize() - off;
+      size = m_io.FSize() - off;
 
    ssize_t bytes_read = 0;
    ssize_t retval = 0;
@@ -97,7 +101,6 @@ int IOEntireFile::Read (char *buff, long long off, int size)
    clLog()->Debug(XrdCl::AppMsg, "IO::Read() read from prefetch retval =  %d %s", retval, m_io.Path());
    if (retval > 0)
    {
-
       bytes_read += retval;
       buff += retval;
       size -= retval;
diff --git a/src/XrdFileCache/XrdFileCacheIOFileBlock.cc b/src/XrdFileCache/XrdFileCacheIOFileBlock.cc
index d01846838ad..ed3e54c4b24 100644
--- a/src/XrdFileCache/XrdFileCacheIOFileBlock.cc
+++ b/src/XrdFileCache/XrdFileCacheIOFileBlock.cc
@@ -126,16 +126,21 @@ bool IOFileBlock::ioActive()
 //______________________________________________________________________________
 int IOFileBlock::Read (char *buff, long long off, int size)
 {
+   // protect from reads over the file size
+   if (off >= m_io.FSize() || off < 0)
+   {
+      errno = EINVAL;
+      return -1;
+   }
+   if (off + size > m_io.FSize())
+      size = m_io.FSize() - off;
+
    long long off0 = off;
    int idx_first = off0/m_blocksize;
    int idx_last = (off0+size-1)/m_blocksize;
    int bytes_read = 0;
    clLog()->Debug(XrdCl::AppMsg, "IOFileBlock::Read() %lld@%d block range [%d-%d] \n %s", off, size, idx_first, idx_last, m_io.Path());
 
-   // protect from reads over the file size
-   if (off + size > m_io.FSize())
-       size =  m_io.FSize() - off;
-
    for (int blockIdx = idx_first; blockIdx <= idx_last; ++blockIdx )
    {
       // locate block