diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index 4c255ad47869..c09def1fceae 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -441,6 +441,10 @@ EOF
         }
     }
 
+    # Don't emit tmpfs entry for /tmp, because it most likely comes from the
+    # boot.tmpOnTmpfs option in configuration.nix (managed declaratively).
+    next if ($mountPoint eq "/tmp" && $fsType eq "tmpfs");
+
     # Emit the filesystem.
     $fileSystems .= <<EOF;
   fileSystems.\"$mountPoint\" =