diff --git a/scripts/build_spack_package.sh b/scripts/build_spack_package.sh
index d5fe48d8c9330208aea74e89e8147d9162c2ceef..0eeb151351aa466c1728c44ff6fbd4c150cde964 100755
--- a/scripts/build_spack_package.sh
+++ b/scripts/build_spack_package.sh
@@ -7,7 +7,7 @@ set -Eeuo pipefail
 if [[ "$#" -ne 2 ]]; then
     echo "Builds the in-repo Spack package of Arbor against the latest Spack release or a given Spack branch"
     echo "usage: build_spack_package.sh arbor_source_directory latest_release|develop"
-	exit 1
+    exit 1
 fi
 
 trap cleanup SIGINT SIGTERM ERR EXIT
@@ -34,17 +34,17 @@ SPACK_VERSION=$2 # latest_release or develop
 SPACK_BRANCH=develop # only used for develop
 
 case $SPACK_VERSION in
-	"develop")
-		git clone --depth 1 --branch $SPACK_BRANCH $SPACK_REPO $SPACK_DIR
-		;;
-	"latest_release")
-		wget "$(curl -sH "Accept: application/vnd.github.v3+json" https://api.github.com/repos/spack/spack/releases/latest | grep browser_download_url |  cut -d '"' -f 4)"
-		tar xfz spack*.tar.gz
-		ln -s spack*/ $SPACK_DIR
-		;;
-	*)
-		echo "SPACK_VERSION" must be \"latest_release\" or \"develop\"
-		exit 1
+    "develop")
+        git clone --depth 1 --branch $SPACK_BRANCH $SPACK_REPO $SPACK_DIR
+        ;;
+    "latest_release")
+        wget "$(curl -sH "Accept: application/vnd.github.v3+json" https://api.github.com/repos/spack/spack/releases/latest | grep browser_download_url |  cut -d '"' -f 4)"
+        tar xfz spack*.tar.gz
+        ln -s spack*/ $SPACK_DIR
+        ;;
+    *)
+        echo "SPACK_VERSION" must be \"latest_release\" or \"develop\"
+        exit 1
 esac
 source $SPACK_DIR/share/spack/setup-env.sh
 spack repo create $SPACK_CUSTOM_REPO
diff --git a/spack/package.py b/spack/package.py
index 94b9e78cfabcc8f542a8a450c54fe222365463bc..259c0ce8f0a56599d9b1a2a06c31c7da0df7d0c1 100644
--- a/spack/package.py
+++ b/spack/package.py
@@ -36,6 +36,7 @@ class Arbor(CMakePackage, CudaPackage):
     depends_on('cmake@3.12:', type='build')
 
     # misc dependencies
+    depends_on('fmt@7.1:', when='@0.5.3:') # required by the modcc compiler
     depends_on('nlohmann-json')
     depends_on('cuda@10:', when='+cuda')
     depends_on('libxml2', when='+neuroml')