@@ -814,15 +814,17 @@ void simplecpp::TokenList::constFoldQuestionOp(Token **tok1) {
         gotoTok1 = false;
         if (tok->str != "?")
             continue;
-        if (!tok->previous || !tok->previous->number)
-            continue;
-        if (!tok->next)
+        if (!tok->previous || !tok->next || !tok->next->next)
+            throw std::runtime_error("invalid expression");
+        if (!tok->previous->number)
             continue;
-        if (!tok->next->next || tok->next->next->op != ':')
+        if (tok->next->next->op != ':')
             continue;
         Token * const condTok = tok->previous;
         Token * const trueTok = tok->next;
         Token * const falseTok = trueTok->next->next;
+        if (!falseTok)
+            throw std::runtime_error("invalid expression");
         if (condTok == *tok1)
             *tok1 = (condTok->str != "0" ? trueTok : falseTok);
         deleteToken(condTok->next); // ?
 
@@ -124,7 +124,11 @@ static std::string testConstFold(const char code[]) {
     std::istringstream istr(code);
     std::vector<std::string> files;
     simplecpp::TokenList expr(istr, files);
-    expr.constFold();
+    try {
+        expr.constFold();
+    } catch (std::exception &) {
+        return "exception";
+    }
     return expr.stringify();
 }
 
@@ -173,6 +177,8 @@ static void constFold() {
     ASSERT_EQUALS("29", testConstFold("13 ^ 16"));
     ASSERT_EQUALS("25", testConstFold("24 | 1"));
     ASSERT_EQUALS("2", testConstFold("1?2:3"));
+    ASSERT_EQUALS("exception", testConstFold("!1 ? 2 :"));
+    ASSERT_EQUALS("exception", testConstFold("?2:3"));
 }
 
 void define1() {