diff --git a/swift/logging/SwiftDiagnostics.cpp b/swift/logging/SwiftDiagnostics.cpp
index 0c3ae0fe88e..9a20830e1ff 100644
--- a/swift/logging/SwiftDiagnostics.cpp
+++ b/swift/logging/SwiftDiagnostics.cpp
@@ -5,8 +5,17 @@
 #include "absl/strings/str_join.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_split.h"
+#include "swift/logging/SwiftAssert.h"
 
 namespace codeql {
+
+namespace {
+Logger& logger() {
+  static Logger ret{"diagnostics"};
+  return ret;
+}
+}  // namespace
+
 void SwiftDiagnosticsSource::emit(std::ostream& out,
                                   std::string_view timestamp,
                                   std::string_view message) const {
@@ -36,6 +45,10 @@ std::string SwiftDiagnosticsSource::sourceId() const {
   std::replace(ret.begin(), ret.end(), '_', '-');
   return ret;
 }
+void SwiftDiagnosticsSource::inscribeImpl(const SwiftDiagnosticsSource* source) {
+  auto [it, inserted] = map().emplace(source->id, source);
+  CODEQL_ASSERT(inserted, "duplicate diagnostics source detected with id {}", source->id);
+}
 
 void SwiftDiagnosticsDumper::write(const char* buffer, std::size_t bufferSize) {
   binlog::Range range{buffer, bufferSize};
diff --git a/swift/logging/SwiftDiagnostics.h b/swift/logging/SwiftDiagnostics.h
index 73e81af26bf..566b56ad99a 100644
--- a/swift/logging/SwiftDiagnostics.h
+++ b/swift/logging/SwiftDiagnostics.h
@@ -31,10 +31,7 @@ struct SwiftDiagnosticsSource {
   template <const SwiftDiagnosticsSource* Spec>
   static void inscribe() {
     static std::once_flag once;
-    std::call_once(once, [] {
-      auto [it, inserted] = map().emplace(Spec->id, Spec);
-      assert(inserted);
-    });
+    std::call_once(once, inscribeImpl, Spec);
   }
 
   // gets a previously inscribed SwiftDiagnosticsSource for the given id. Will abort if none exists
@@ -47,6 +44,8 @@ struct SwiftDiagnosticsSource {
   void emit(std::ostream& out, std::string_view timestamp, std::string_view message) const;
 
  private:
+  static void inscribeImpl(const SwiftDiagnosticsSource* Spec);
+
   std::string sourceId() const;
   using Map = std::unordered_map<std::string, const SwiftDiagnosticsSource*>;