diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index 2d0acca24..43245f61c 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -76,7 +76,7 @@ Logger * makeDefaultLogger()
     return new SimpleLogger();
 }
 
-std::atomic<uint64_t> Activity::nextId{(uint64_t) getpid() << 32};
+std::atomic<uint64_t> nextId{(uint64_t) getpid() << 32};
 
 Activity::Activity() : id(nextId++) { };
 
diff --git a/src/libutil/logging.hh b/src/libutil/logging.hh
index ddfc336fe..9ef6e3ee3 100644
--- a/src/libutil/logging.hh
+++ b/src/libutil/logging.hh
@@ -15,7 +15,6 @@ typedef enum {
 
 class Activity
 {
-    static std::atomic<uint64_t> nextId;
 public:
     typedef uint64_t t;
     const t id;
diff --git a/src/nix/progress-bar.cc b/src/nix/progress-bar.cc
index 24e435f81..2ecbea8ee 100644
--- a/src/nix/progress-bar.cc
+++ b/src/nix/progress-bar.cc
@@ -24,6 +24,7 @@ private:
         std::string uri;
         uint64_t current = 0;
         uint64_t expected = 0;
+        DownloadInfo(const std::string & uri) : uri(uri) { }
     };
 
     struct State