diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 49865aa90..7269bdba5 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -622,7 +622,7 @@ ProcessLineResult NixRepl::processLine(std::string line)
             // TODO: this only shows a progress bar for explicitly initiated builds,
             // not eval-time fetching or builds performed for IFD.
             // But we can't just show it everywhere, since that would erase partial output from evaluation.
-            startProgressBar();
+            logger->resume();
             Finally stopLogger([&]() {
                 stopProgressBar();
             });
diff --git a/src/libmain/progress-bar.cc b/src/libmain/progress-bar.cc
index d83b09cd4..6b5fcdef8 100644
--- a/src/libmain/progress-bar.cc
+++ b/src/libmain/progress-bar.cc
@@ -82,6 +82,22 @@ private:
         bool haveUpdate = true;
     };
 
+    void createUpdateThread()
+    {
+        this->updateThread = std::thread([&]() {
+            auto state(state_.lock());
+            auto nextWakeup = A_LONG_TIME;
+            while (state->active) {
+                if (!state->haveUpdate) {
+                    state.wait_for(updateCV, nextWakeup);
+                }
+
+                nextWakeup = draw(*state);
+                state.wait_for(quitCV, std::chrono::milliseconds(50));
+            }
+        });
+    }
+
     Sync<State> state_;
 
     std::thread updateThread;
@@ -97,16 +113,7 @@ public:
         : isTTY(isTTY)
     {
         state_.lock()->active = isTTY;
-        updateThread = std::thread([&]() {
-            auto state(state_.lock());
-            auto nextWakeup = A_LONG_TIME;
-            while (state->active) {
-                if (!state->haveUpdate)
-                    state.wait_for(updateCV, nextWakeup);
-                nextWakeup = draw(*state);
-                state.wait_for(quitCV, std::chrono::milliseconds(50));
-            }
-        });
+        this->createUpdateThread();
     }
 
     ~ProgressBar()
@@ -133,10 +140,21 @@ public:
         writeToStderr("\r\e[K");
     }
 
-    void resume() override {
-        state_.lock()->paused = false;
-        writeToStderr("\r\e[K");
-        state_.lock()->haveUpdate = true;
+    void resume() override
+    {
+        {
+            auto lockedState(this->state_.lock());
+            lockedState->paused = false;
+            writeToStderr("\r\e[K");
+            lockedState->haveUpdate = true;
+        }
+
+        // We must lock individually here, as createUpdateThread() also locks.
+        if (!state_.lock()->active) {
+            state_.lock()->active = true;
+            this->createUpdateThread();
+        }
+
         updateCV.notify_one();
     }