diff --git a/find-file-doc-comments.pl b/find-file-doc-comments.pl
index e14028f..bb46662 100755
--- a/find-file-doc-comments.pl
+++ b/find-file-doc-comments.pl
@@ -32,6 +32,7 @@ exit main(@ARGV);
 sub main {
     die "Need a filename" unless @_;
     my $filename = shift;
+    die "Could not read $filename" unless -r $filename;
     say "Processing file $filename" if $VERBOSE;
 
     # Fatalize all warnings, and log which file triggered the warning.