diff --git a/src/cdf/core/configuration.py b/src/cdf/core/configuration.py
index 051c927..b363616 100644
--- a/src/cdf/core/configuration.py
+++ b/src/cdf/core/configuration.py
@@ -223,6 +223,8 @@ def apply_converters(
                     raise ValueError(
                         "Resolver instance not provided but found @resolve converter"
                     )
+                if transformed_value not in resolver:
+                    raise ValueError(f"Key not found in resolver: {transformed_value}")
                 transformed_value = resolver[transformed_value]
                 continue
             transformed_value = _CONVERTERS[converter.lower()](transformed_value)
diff --git a/tests/core/injector/test_config.py b/tests/core/injector/test_config.py
index 3241c55..c50e132 100644
--- a/tests/core/injector/test_config.py
+++ b/tests/core/injector/test_config.py
@@ -83,3 +83,5 @@ def bar(user: str, password: str, database: str):
 
     bar_configured = resolver.resolve_defaults(bar)
     assert bar_configured() == ("someone", "secret", "test")
+
+    assert "main_api" in resolver