diff --git a/pkgs/applications/emulators/simh/default.nix b/pkgs/applications/emulators/simh/default.nix
index 1e939538cda..6f3409ec063 100644
--- a/pkgs/applications/emulators/simh/default.nix
+++ b/pkgs/applications/emulators/simh/default.nix
@@ -22,6 +22,11 @@ stdenv.mkDerivation rec {
 
   dontConfigure = true;
 
+  # Workaround to build against upstream gcc-10 and clang-11.
+  # Can be removed when next release contains
+  #    https://github.com/simh/simh/issues/794
+  NIX_CFLAGS_COMPILE = [ "-fcommon" ];
+
   makeFlags = [ "GCC=${stdenv.cc.targetPrefix}cc" "CC_STD=-std=c99" "LDFLAGS=-lm" ];
 
   preInstall = ''