diff --git a/README.md b/README.md
index 2cc4f885..eaed52fe 100644
--- a/README.md
+++ b/README.md
@@ -190,6 +190,10 @@ with key suffixes as follows:
  * `_required`: `true` means that the key must be set
  * `_values`: the value, if set, must be within the space-separated list
    of values here
+ * `_type`: `path` means the value, if set, must be the path to a file which
+   exists
+ * `_type`: `paths` means the value, if set, must be a space-separated list of
+   path to files which exist
 
 Merged options
 --------------
diff --git a/config/schema.ini b/config/schema.ini
index 01d4eafa..c5cd7147 100644
--- a/config/schema.ini
+++ b/config/schema.ini
@@ -4,6 +4,9 @@
 #  _required = true means that the key must be set
 #  _values means the value, if set, must be within the space-separated list of
 #          values here
+#  _type = path means the value, if set, must be the path to a file which exists
+#  _type = paths means the value, if set, must be a space-separated list of
+#                path to files which exist
 
 [image]
 compression_required = true
diff --git a/run-build b/run-build
index 4141e522..33323ea1 100755
--- a/run-build
+++ b/run-build
@@ -515,6 +515,27 @@ class ImageBuilder(object):
                 raise eib.ImageBuildError(
                     'Configuration key [%s] %s has invalid value: %s'
                     % (section, option, self.config[section][option]))
+        elif option.endswith('_type'):
+            real_option = option[:-len('_type')]
+            if real_option in self.config[section]:
+                real_value = self.config[section][real_option].strip()
+                match value:
+                    case "path":
+                        paths = [real_value] if real_value else []
+                    case "paths":
+                        paths = real_value.split()
+                    case other:
+                        raise eib.ImageBuildError(
+                            f'Schema key [{section}] {option} has invalid value: '
+                            f'{value}'
+                        )
+
+                for path in paths:
+                    if not os.path.exists(path):
+                        raise eib.ImageBuildError(
+                            f'Configuration key [{section}] {real_option} refers to '
+                            f'nonexistent path: {path}'
+                        )
 
     def check_config(self):
         """Check loaded configuration against schema for validity."""