diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 72e9d0af4..004381ea4 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -5331,6 +5331,8 @@ static void valueFlowForwardConst(Token* start,
                                   const Settings* const settings,
                                   int /*unused*/ = 0)
 {
+    if (!precedes(start, end))
+        throw InternalError(var->nameToken(), "valueFlowForwardConst: start token does not precede the end token.");
     for (Token* tok = start; tok != end; tok = tok->next()) {
         if (tok->varId() == var->declarationId()) {
             for (const ValueFlow::Value& value : values)