--- a/browser/installer/windows/nsis/stub.nsi
+++ b/browser/installer/windows/nsis/stub.nsi
@@ -1432,17 +1432,20 @@ Function CheckInstall
     System::Call 'kernel32::CloseHandle(i $HandleDownload)'
     StrCpy $ExitCode "${ERR_INSTALL_TIMEOUT}"
     ; Use a timer so the UI has a chance to update
     ${NSD_CreateTimer} DisplayDownloadError ${InstallIntervalMS}
     Return
   ${EndIf}
 
   ${If} $ProgressCompleted < ${PROGRESS_BAR_INSTALL_END_STEP}
-    IntOp $ProgressCompleted $ProgressCompleted + 1
+    IntOp $0 ${PROGRESS_BAR_INSTALL_END_STEP} - ${PROGRESS_BAR_DOWNLOAD_END_STEP}
+    IntOp $0 $InstallCounterStep * $0
+    IntOp $0 $0 / $InstallTotalSteps
+    IntOp $ProgressCompleted ${PROGRESS_BAR_DOWNLOAD_END_STEP} + $0
     Call SetProgressBars
   ${EndIf}
 
   ${If} ${FileExists} "$INSTDIR\install.log"
     Delete "$INSTDIR\install.tmp"
     CopyFiles /SILENT "$INSTDIR\install.log" "$INSTDIR\install.tmp"
 
     ; The unfocus and refocus that happens approximately here is caused by the