diff --git a/src/muscle-tab.c b/src/muscle-tab.c
index e1f6ee4b..6d48d014 100644
--- a/src/muscle-tab.c
+++ b/src/muscle-tab.c
@@ -37,7 +37,7 @@ muscle_kind_new (char const *k)
     return muscle_keyword;
   else if (STREQ (k, "string"))
     return muscle_string;
-  aver (0);
+  abort ();
 }
 
 char const *
@@ -49,7 +49,7 @@ muscle_kind_string (muscle_kind k)
     case muscle_keyword: return "keyword";
     case muscle_string:  return "string";
     }
-  aver (0);
+  abort ();
 }
 
 
diff --git a/src/scan-skel.l b/src/scan-skel.l
index 06a13665..efada879 100644
--- a/src/scan-skel.l
+++ b/src/scan-skel.l
@@ -192,7 +192,7 @@ flag (const char *arg)
   else if (STREQ (arg, "warn"))
     return Wother;
   else
-    aver (false);
+    abort ();
 }
 
 static void