diff --git a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
--- a/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ b/clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -4002,6 +4002,19 @@
   EXPECT_EQ(Second.activeParameter, 1);
 }
 
+TEST(CompletionTest, DoNotCrash) {
+  llvm::StringLiteral Cases[] = {
+      R"cpp(
+    template <typename = int> struct Foo {};
+    auto a = [x(3)](Foo<^>){};
+    )cpp",
+  };
+  for (auto Case : Cases) {
+    SCOPED_TRACE(Case);
+    auto Completions = completions(Case);
+  }
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang
diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -226,6 +226,11 @@
   if (ShouldGenerateLocation(D) && GenLoc(D, /*IncludeOffset=*/isLocal(D)))
     return;
 
+  if (D->getType().isNull()) {
+    IgnoreResults = true;
+    return;
+  }
+
   const unsigned StartSize = Buf.size();
   VisitDeclContext(D->getDeclContext());
   if (Buf.size() == StartSize)