diff --git a/promenade/cli.py b/promenade/cli.py
index 694f3e05..9bd3e015 100644
--- a/promenade/cli.py
+++ b/promenade/cli.py
@@ -31,7 +31,10 @@ def build_all(*, config_files, output_dir, validators):
     debug = _debug()
     try:
         c = config.Configuration.from_streams(
-            debug=debug, streams=config_files)
+            debug=debug,
+            substitute=True,
+            allow_missing_substitutions=False,
+            streams=config_files)
         b = builder.Builder(c, validators=validators)
         b.build_all(output_dir=output_dir)
     except exceptions.PromenadeException as e:
@@ -52,7 +55,11 @@ def genereate_certs(*, config_files, output_dir):
     debug = _debug()
     try:
         c = config.Configuration.from_streams(
-            debug=debug, streams=config_files, substitute=True, validate=False)
+            debug=debug,
+            streams=config_files,
+            substitute=True,
+            allow_missing_substitutions=True,
+            validate=False)
         g = generator.Generator(c)
         g.generate(output_dir)
     except exceptions.PromenadeException as e:
diff --git a/promenade/config.py b/promenade/config.py
index 9205770c..8886bb75 100644
--- a/promenade/config.py
+++ b/promenade/config.py
@@ -18,6 +18,7 @@ class Configuration:
                  documents,
                  debug=False,
                  substitute=True,
+                 allow_missing_substitutions=True,
                  validate=True):
         LOG.info("Parsing document schemas.")
         schema_set = validation.load_schemas_from_docs(documents)
@@ -29,12 +30,12 @@ class Configuration:
                 deckhand_eng = layering.DocumentLayering(
                     documents,
                     substitution_sources=documents,
-                    fail_on_missing_sub_src=False)
+                    fail_on_missing_sub_src=not allow_missing_substitutions)
                 documents = [dict(d) for d in deckhand_eng.render()]
             except dh_errors.DeckhandException as e:
-                LOG.exception(str(e))
-                LOG.error('An unknown Deckhand exception occurred while trying'
-                          ' to render documents.')
+                LOG.exception(
+                    'An unknown Deckhand exception occurred while trying'
+                    ' to render documents.')
                 raise exceptions.DeckhandException(str(e))
 
             LOG.info("Deckhand engine returned %d documents." % len(documents))
diff --git a/promenade/control/join_scripts.py b/promenade/control/join_scripts.py
index 957ad6e3..83bf241e 100644
--- a/promenade/control/join_scripts.py
+++ b/promenade/control/join_scripts.py
@@ -43,7 +43,8 @@ class JoinScriptsResource(BaseResource):
         join_ip = _get_join_ip()
 
         try:
-            config = Configuration.from_design_ref(design_ref)
+            config = Configuration.from_design_ref(
+                design_ref, allow_missing_substitutions=False)
         except exceptions.DeckhandException as e:
             raise falcon.HTTPInternalServerError(description=str(e))