diff --git a/src/PVE/API2/Storage/Status.pm b/src/PVE/API2/Storage/Status.pm
index f86e5d3..47f82d7 100644
--- a/src/PVE/API2/Storage/Status.pm
+++ b/src/PVE/API2/Storage/Status.pm
@@ -510,6 +510,10 @@ __PACKAGE__->register_method ({
 			die "checksum mismatch: got '$checksum_got' != expect '$checksum'\n";
 		    }
 		}
+
+		if ($content eq 'iso') {
+		    PVE::Storage::assert_iso_content($tmpfilename);
+		}
 	    };
 	    if (my $err = $@) {
 		# unlinks only the temporary file from the http server
@@ -662,6 +666,14 @@ __PACKAGE__->register_method({
 	    $opts->{hash_required} = 1;
 	}
 
+	$opts->{assert_file_validity} = sub {
+	    my ($tmp_path) = @_;
+
+	    if ($content eq 'iso') {
+		PVE::Storage::assert_iso_content($tmp_path);
+	    }
+	};
+
 	my $worker = sub {
 	    if ($compression) {
 		die "decompression not supported for $content\n" if $content ne 'iso';
diff --git a/src/PVE/Storage.pm b/src/PVE/Storage.pm
index b876651..1c4c5cd 100755
--- a/src/PVE/Storage.pm
+++ b/src/PVE/Storage.pm
@@ -2196,4 +2196,14 @@ sub get_import_metadata {
     return $plugin->get_import_metadata($scfg, $volname, $storeid);
 }
 
+# dies if the content of the given path is unexpected for an ISO
+sub assert_iso_content {
+    my ($path) = @_;
+
+    # check for things like backing image
+    file_size_info($path, undef, 1);
+
+    return 1;
+}
+
 1;