diff --git a/pkgs/os-specific/bsd/netbsd/compat-setup-hook.sh b/pkgs/os-specific/bsd/netbsd/compat-setup-hook.sh
index 3c49337a937c..acd90b7aa2f0 100644
--- a/pkgs/os-specific/bsd/netbsd/compat-setup-hook.sh
+++ b/pkgs/os-specific/bsd/netbsd/compat-setup-hook.sh
@@ -3,4 +3,3 @@ getHostRole
 
 export NIX_LDFLAGS${role_post}+=" -lnbcompat"
 export NIX_CFLAGS_COMPILE${role_post}+=" -DHAVE_NBTOOL_CONFIG_H"
-export NIX_CFLAGS_COMPILE${role_post}+=" -include nbtool_config.h"
diff --git a/pkgs/os-specific/bsd/netbsd/default.nix b/pkgs/os-specific/bsd/netbsd/default.nix
index beaa176dae15..7a6604afe641 100644
--- a/pkgs/os-specific/bsd/netbsd/default.nix
+++ b/pkgs/os-specific/bsd/netbsd/default.nix
@@ -120,7 +120,17 @@ in lib.makeScopeWithSplicing
   } // lib.optionalAttrs (attrs.headersOnly or false) {
     installPhase = "includesPhase";
     dontBuild = true;
-  } // attrs));
+  } // attrs // {
+    postPatch = lib.optionalString (!stdenv'.hostPlatform.isNetBSD) ''
+      # Files that use NetBSD-specific macros need to have nbtool_config.h
+      # included ahead of them on non-NetBSD platforms.
+      set +e
+      grep -Zlr "^__RCSID
+      ^__BEGIN_DECLS" | xargs -0r grep -FLZ nbtool_config.h |
+          xargs -0tr sed -i '0,/^#/s//#include <nbtool_config.h>\n\0/'
+      set -e
+    '' + attrs.postPatch or "";
+  }));
 
   ##
   ## START BOOTSTRAPPING