Use "true" instead of an empty command
diff --git a/ninja.go b/ninja.go
index 48cea9b..2408ebf 100644
--- a/ninja.go
+++ b/ninja.go
@@ -75,6 +75,9 @@
 		cmd = strings.TrimRight(cmd, " \t\n;")
 		cmd = strings.Replace(cmd, "$", "$$", -1)
 		cmd = strings.Replace(cmd, "\t", " ", -1)
+		if cmd == "" {
+			cmd = "true"
+		}
 		buf.WriteString(cmd)
 		if i == len(runners)-1 && r.ignoreError {
 			buf.WriteString(" ; true")