diff --git a/bin/build-spack-env.sh b/bin/build-spack-env.sh
index 4b04a27..12c1e6e 100755
--- a/bin/build-spack-env.sh
+++ b/bin/build-spack-env.sh
@@ -360,7 +360,7 @@ EOF
 _cache_info() {
   if [[ "$cache_spec" =~ ^(([^|]+)\|)?((source|binary):)?(.*)$ ]]; then
     cache_name="${BASH_REMATCH[2]:-buildcache_$((++cache_count))}"
-    cache_type="${BASH_REMATCH[4]}"
+    (( have_mirror_add_type )) && cache_type="${BASH_REMATCH[4]}"
     cache_url="${BASH_REMATCH[5]}"
   else
     _die $EXIT_SPACK_CONFIG_FAILURE "unable to parse cache_spec \"$cache_spec\""
@@ -528,6 +528,12 @@ _configure_spack() {
     buildcache_rel_arg="-r"
   ####################################
 
+  ####################################
+  # Check whether spack mirror add supports --type
+  mirror_add_help="$(spack mirror add --help | grep -Ee '^[[:space:]]--type[[:space:]]+')"
+  [ -n "$mirror_add_help" ] && have_mirror_add_type=1
+  ####################################
+
   ####################################
   # Make sure we know about compilers.
   _report $PROGRESS "configuring compilers"