diff --git a/taglib/flac/flacfile.cpp b/taglib/flac/flacfile.cpp
index ada215db..6ecd3bad 100644
--- a/taglib/flac/flacfile.cpp
+++ b/taglib/flac/flacfile.cpp
@@ -497,6 +497,11 @@ void FLAC::File::scan()
 
     seek(nextBlockOffset);
     const ByteVector header = readBlock(4);
+    if(header.size() != 4) {
+      debug("FLAC::File::scan() -- Failed to read a block header");
+      setValid(false);
+      return;
+    }
 
     // Header format (from spec):
     // <1> Last-metadata-block flag