diff --git a/source/org/thdl/tib/text/ttt/TParseTree.java b/source/org/thdl/tib/text/ttt/TParseTree.java
index 00250e7..36c190b 100644
--- a/source/org/thdl/tib/text/ttt/TParseTree.java
+++ b/source/org/thdl/tib/text/ttt/TParseTree.java
@@ -304,7 +304,7 @@ class TParseTree {
                             if (warningLevel == "All")
                                 return "Warning: The last stack does not have a vowel in the ACIP {" + ((null != originalACIP) ? originalACIP : recoverACIP()) + "}; this may indicate a typo, because Sanskrit, which this is (because it's not legal Tibetan), should have a vowel after each stack.";
                         } else {
-                            return "Warning: There is a stack, before the last stack, without a vowel in the ACIP {" + ((null != originalACIP) ? originalACIP : recoverACIP()) + "}; this may indicate a typo, because Sanskrit, which this is (because it's not legal Tibetan), should have a vowel after each stack.";
+                            throw new Error("Can't happen now that we stack greedily");
                         }
                     }
                     if ("All" == warningLevel) {
@@ -317,7 +317,7 @@ class TParseTree {
                         if (warningLevel == "All")
                             return "Warning: The last stack does not have a vowel in the ACIP {" + ((null != originalACIP) ? originalACIP : recoverACIP()) + "}; this may indicate a typo, because Sanskrit, which this is (because it's not legal Tibetan), should have a vowel after each stack.";
                     } else {
-                        return "Warning: There is a stack, before the last stack, without a vowel in the ACIP {" + ((null != originalACIP) ? originalACIP : recoverACIP()) + "}; this may indicate a typo, because Sanskrit, which this is (because it's not legal Tibetan), should have a vowel after each stack.";
+                        throw new Error("Can't happen now that we stack greedily");
                     }
                 }
             }
diff --git a/source/org/thdl/tib/text/ttt/TStackList.java b/source/org/thdl/tib/text/ttt/TStackList.java
index e624bb6..0b34760 100644
--- a/source/org/thdl/tib/text/ttt/TStackList.java
+++ b/source/org/thdl/tib/text/ttt/TStackList.java
@@ -203,8 +203,11 @@ class TStackList {
             if (null == lastPair.getRight()
                 && !((l = lastPair.getLeft()) != null && l.length() == 1
                      && l.charAt(0) >= '0' && l.charAt(0) <= '9')) {
-                if (null != isLastStack)
+                if (null != isLastStack) {
                     isLastStack[0] = (i + 1 == size());
+                    if (!isLastStack[0])
+                        throw new Error("But we now stack greedily!");
+                }
                 return true;
             }
         }