diff --git a/laymanshex.go b/laymanshex.go
index 21d1f88..bece35c 100644
--- a/laymanshex.go
+++ b/laymanshex.go
@@ -178,9 +178,9 @@ func (part *filePart) setByteFieldHandling(assignments map[string]*formatAssignm
 			ass.used = true
 			err = nil
 		} else {
-			msg := "byte field: could neither parse size to int64 nor obtain value from -fvar"
+			msg := "byte field definition in format description: could neither parse size to int64 nor obtain value from -fvar"
 			if part.name != "" {
-				msg += " definition " + part.name
+				msg += " - definition of " + part.name
 			}
 			err = errors.New(msg)
 		}