diff --git a/lib/IDE/CodeCompletion.cpp b/lib/IDE/CodeCompletion.cpp
index c984e9291ed..eca6635783e 100644
--- a/lib/IDE/CodeCompletion.cpp
+++ b/lib/IDE/CodeCompletion.cpp
@@ -1009,6 +1009,8 @@ public:
                                                    TopConformances.end());
     while (!Worklist.empty()) {
       auto Conformance = Worklist.pop_back_val();
+      if (!Conformance->isComplete())
+        continue;
       Conformance->forEachTypeWitness(TypeResolver.get(),
                                       [&](const AssociatedTypeDecl *ATD,
                                           const Substitution &Subst) -> bool {