diff --git a/trajopt/src/collision_terms.cpp b/trajopt/src/collision_terms.cpp
index 0595f35e..8f372cfb 100644
--- a/trajopt/src/collision_terms.cpp
+++ b/trajopt/src/collision_terms.cpp
@@ -799,7 +799,7 @@ void CollisionEvaluator::CalcDistExpressionsSingleTimeStepW(const DblVec& x,
 {
   ContactResultMapConstPtr dist_results = GetContactResultMapCached(x);
   CollisionsToDistanceExpressionsW(exprs, exprs_data, *dist_results, vars0_, x, false);
-  assert(dist_results->count() == exprs.size());
+  assert(dist_results->size() == exprs.size());
 
   for (auto& expr : exprs)
     expr = sco::cleanupAff(expr);