diff --git a/src/SymbolTable.cc b/src/SymbolTable.cc
index d836566dc08272978d9f77e79f1bfc5f4095b897..94045162ae2fc4e8147163285caf0a085e6b7a2b 100644
--- a/src/SymbolTable.cc
+++ b/src/SymbolTable.cc
@@ -827,7 +827,7 @@ void
 SymbolTable::addObservedExogenousVariable(int symb_id) noexcept(false)
 {
   validateSymbID(symb_id);
-  assert(getType(symb_id) != SymbolType::endogenous);
+  assert(getType(symb_id) == SymbolType::exogenous);
   varexobs.push_back(symb_id);
 }