diff --git a/board/common/lib.sh b/board/common/lib.sh
index 1c8d7dee..affa806e 100644
--- a/board/common/lib.sh
+++ b/board/common/lib.sh
@@ -9,11 +9,20 @@ die()
     exit 1
 }
 
+# Find all matching key=value assignments in output/.config
+# E.g., load_cfg DISK_IMAGE sets the following variables:
+#
+#      DISK_IMAGE=y
+#      DISK_IMAGE_SIZE="512"
+#      etc.
+#
+# shellcheck disable=SC1090
 load_cfg()
 {
-    local tmp=$(mktemp -p /tmp)
+    tmp=$(mktemp -p /tmp)
 
-    grep "$1" $BR2_CONFIG >$tmp
-    .  $tmp
-    rm $tmp
+    grep -E "${1}.*=" "$BR2_CONFIG" >"$tmp"
+    .  "$tmp"
+
+    rm "$tmp"
 }
diff --git a/board/common/post-image.sh b/board/common/post-image.sh
index 57185e2f..9fddbf5c 100755
--- a/board/common/post-image.sh
+++ b/board/common/post-image.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 common=$(dirname "$(readlink -f "$0")")
-. $common/lib.sh
+. "$common/lib.sh"
 
 load_cfg BR2_ARCH
 load_cfg BR2_DEFCONFIG
@@ -50,8 +50,6 @@ fi
 
 load_cfg GNS3_APPLIANCE
 if [ "$GNS3_APPLIANCE" = "y" ]; then
-    load_cfg GNS3_APPLIANCE_RAM
-    load_cfg GNS3_APPLIANCE_IFNUM
     ixmsg "Creating GNS3 Appliance, $GNS3_APPLIANCE_RAM MiB with $GNS3_APPLIANCE_IFNUM ports"
     $common/mkgns3a.sh $NAME $GNS3_APPLIANCE_RAM $GNS3_APPLIANCE_IFNUM
 fi