diff --git a/src/qt/modaloverlay.cpp b/src/qt/modaloverlay.cpp
--- a/src/qt/modaloverlay.cpp
+++ b/src/qt/modaloverlay.cpp
@@ -73,7 +73,6 @@
 
     // show progress speed if we have more then one sample
     if (blockProcessTime.size() >= 2) {
-        double progressStart = blockProcessTime[0].second;
         double progressDelta = 0;
         double progressPerHour = 0;
         qint64 timeDelta = 0;
@@ -85,11 +84,14 @@
             // take first sample after 500 seconds or last available one
             if (sample.first < (currentDate.toMSecsSinceEpoch() - 500 * 1000) ||
                 i == blockProcessTime.size() - 1) {
-                progressDelta = progressStart - sample.second;
+                progressDelta = blockProcessTime[0].second - sample.second;
                 timeDelta = blockProcessTime[0].first - sample.first;
                 progressPerHour =
                     progressDelta / (double)timeDelta * 1000 * 3600;
-                remainingMSecs = remainingProgress / progressDelta * timeDelta;
+                remainingMSecs =
+                    (progressDelta > 0)
+                        ? remainingProgress / progressDelta * timeDelta
+                        : -1;
                 break;
             }
         }
@@ -98,13 +100,18 @@
             QString::number(progressPerHour * 100, 'f', 2) + "%");
 
         // show expected remaining time
-        ui->expectedTimeLeft->setText(
-            GUIUtil::formatNiceTimeOffset(remainingMSecs / 1000.0));
+        if (remainingMSecs >= 0) {
+            ui->expectedTimeLeft->setText(
+                GUIUtil::formatNiceTimeOffset(remainingMSecs / 1000.0));
+        } else {
+            ui->expectedTimeLeft->setText(QObject::tr("unknown"));
+        }
 
         static const int MAX_SAMPLES = 5000;
-        if (blockProcessTime.count() > MAX_SAMPLES)
+        if (blockProcessTime.count() > MAX_SAMPLES) {
             blockProcessTime.remove(MAX_SAMPLES,
                                     blockProcessTime.count() - MAX_SAMPLES);
+        }
     }
 
     // show the last block date