diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 08717d34b779..77b3bbb038f2 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -7412,7 +7412,11 @@ in
 
   neko = callPackage ../development/compilers/neko { };
 
-  nextpnr = libsForQt5.callPackage ../development/compilers/nextpnr { };
+  nextpnr = libsForQt5.callPackage ../development/compilers/nextpnr {
+    # QT 5.12 has a weird regression involving the floorplanning window having
+    # a 'blank' or 'transparent' background, so fall back to 5.11 for now.
+    qtbase = qt511.qtbase;
+  };
 
   nasm = callPackage ../development/compilers/nasm { };