diff --git a/metropolis/node/build/mkverity/mkverity.go b/metropolis/node/build/mkverity/mkverity.go
index 7300f49..f44b601 100644
--- a/metropolis/node/build/mkverity/mkverity.go
+++ b/metropolis/node/build/mkverity/mkverity.go
@@ -58,7 +58,7 @@
 		return nil, fmt.Errorf("the data image must be a regular file")
 	}
 	if ds.Size()%int64(bs) != 0 {
-		return nil, fmt.Errorf("the data image must end on a %d-byte block boundary.", bs)
+		return nil, fmt.Errorf("the data image must end on a %d-byte block boundary", bs)
 	}
 
 	// Create an empty hash image file.