diff --git a/build b/build
index 042816c..5e4cf3a 100755
--- a/build
+++ b/build
@@ -215,6 +215,8 @@ so looping over all of them would waste time.
                 'diod',
                 # For prebuilt qcow2 unpack.
                 'qemu-utils',
+                # Otherwise HDF5 not found.
+                'pkg-config',
             },
             'python3_pkgs': {
                 # https://cirosantilli.com/linux-kernel-module-cheat#gem5-config-dot