diff --git a/embedmd/embedmd.go b/embedmd/embedmd.go
index 7135f75..c59cc2a 100644
--- a/embedmd/embedmd.go
+++ b/embedmd/embedmd.go
@@ -105,7 +105,9 @@ func (e *embedder) runCommand(w io.Writer, cmd *command) error {
 	}
 
 	fmt.Fprintln(w, "```"+cmd.lang)
-	w.Write(b)
+	if _, err := w.Write(b); err != nil {
+		return err
+	}
 	fmt.Fprintln(w, "```")
 	return nil
 }
diff --git a/main.go b/main.go
index 6892b2f..c25e5cc 100644
--- a/main.go
+++ b/main.go
@@ -171,8 +171,8 @@ func processFile(path string, rewrite, doDiff bool) (foundDiff bool, err error)
 		return false, f.Truncate(int64(n))
 	}
 
-	io.Copy(stdout, buf)
-	return false, nil
+	_, err = io.Copy(stdout, buf)
+	return false, err
 }
 
 func diff(a, b string) (string, error) {