diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 90be53fc3a0..589e8d8085f 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1487,7 +1487,7 @@ in
 
   dtach = callPackage ../tools/misc/dtach { };
 
-  dtc = callPackage ../development/compilers/dtc { };
+  dtc = callPackage ../development/compilers/dtc { flex = flex_2_6_1; };
 
   dub = callPackage ../development/tools/build-managers/dub { };