diff --git a/gen-signal-names.awk b/gen-signal-names.awk
index f2b3153..7e9142e 100644
--- a/gen-signal-names.awk
+++ b/gen-signal-names.awk
@@ -22,6 +22,7 @@ BEGIN {
             }
         }
     }
+    close(cmd)
     print "};"
     print "#define MIN_SIGNUM " min
     print "#define MAX_SIGNUM " max