diff --git a/java/dev/enola/common/io/resource/ResourceProviders.java b/java/dev/enola/common/io/resource/ResourceProviders.java
index ae1727365..7be14b42f 100644
--- a/java/dev/enola/common/io/resource/ResourceProviders.java
+++ b/java/dev/enola/common/io/resource/ResourceProviders.java
@@ -21,7 +21,6 @@
 
 import dev.enola.common.io.iri.URIs;
 
-import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -71,7 +70,7 @@ public ResourceProviders() {
     }
 
     @Override
-    public @Nullable Resource getResource(final URI uri) {
+    public Resource getResource(final URI uri) {
         var resolvedURI = URIs.absolutify(uri);
 
         for (ResourceProvider resourceProvider : resourceProviders) {
@@ -79,9 +78,8 @@ public ResourceProviders() {
             if (resource != null) return resource;
         }
 
-        // TODO warn instead of debug - or does that create a shitload of logging?
-        LOG.debug("Unsupported URI: {}", resolvedURI);
-        return null;
+        throw new IllegalArgumentException(
+                "Unsupported scheme, but try activating one of the --XYZ-scheme flags: " + uri);
     }
 
     @Override
diff --git a/java/dev/enola/common/io/resource/ResourceProvidersTest.java b/java/dev/enola/common/io/resource/ResourceProvidersTest.java
index a866e0e9c..e00b5999c 100644
--- a/java/dev/enola/common/io/resource/ResourceProvidersTest.java
+++ b/java/dev/enola/common/io/resource/ResourceProvidersTest.java
@@ -223,7 +223,7 @@ public void testNoScheme() {
                 () -> new ResourceProviders().getResource(URI.create("test:something")));
     }
 
-    @Test
+    @Test(expected = IllegalArgumentException.class)
     public void testUnknownScheme() {
         assertThat(new ResourceProviders().getResource(URI.create("xyz-unknown:test"))).isNull();
     }
diff --git a/java/dev/enola/rdf/io/RdfResourceIntoThingConverterTest.java b/java/dev/enola/rdf/io/RdfResourceIntoThingConverterTest.java
index 39ec4e5e8..a96cc3e25 100644
--- a/java/dev/enola/rdf/io/RdfResourceIntoThingConverterTest.java
+++ b/java/dev/enola/rdf/io/RdfResourceIntoThingConverterTest.java
@@ -34,7 +34,7 @@ public class RdfResourceIntoThingConverterTest {
 
     DatatypeRepository datatypeRepository = new DatatypeRepositoryBuilder().build();
     ResourceProvider resourceProvider =
-            new ResourceProviders(new ClasspathResource.Provider(), new FileResource.Provider());
+            new ResourceProviders(new ClasspathResource.Provider(), new EmptyResource.Provider());
     RdfResourceIntoThingConverter c =
             new RdfResourceIntoThingConverter<Thing>(resourceProvider, datatypeRepository);
 
@@ -50,8 +50,8 @@ public void emptyYAML() throws IOException {
     }
 
     @Test
-    public void directory() throws IOException {
-        assertThat(convert(URI.create("file:/tmp/"))).isEmpty();
+    public void empty() throws IOException {
+        assertThat(convert(EmptyResource.EMPTY_URI)).isEmpty();
     }
 
     private Iterable<Thing.Builder<?>> convert(URI uri) throws IOException {