diff --git a/elda-lda/src/main/java/com/epimorphics/lda/core/APIEndpoint.java b/elda-lda/src/main/java/com/epimorphics/lda/core/APIEndpoint.java
index 84e85a9da..54bf21bb2 100755
--- a/elda-lda/src/main/java/com/epimorphics/lda/core/APIEndpoint.java
+++ b/elda-lda/src/main/java/com/epimorphics/lda/core/APIEndpoint.java
@@ -18,6 +18,7 @@
 package com.epimorphics.lda.core;
 
 import com.epimorphics.lda.bindings.Bindings;
+import com.epimorphics.lda.exceptions.BadRequestException;
 import com.epimorphics.lda.query.QueryParameter;
 import com.epimorphics.lda.renderers.Renderer;
 import com.epimorphics.lda.shortnames.CompleteContext;
@@ -26,6 +27,7 @@
 import com.epimorphics.lda.support.NoteBoard;
 import com.epimorphics.util.MediaType;
 import com.epimorphics.util.URIUtils;
+import jakarta.ws.rs.core.UriBuilderException;
 import org.apache.jena.rdf.model.Model;
 import org.apache.jena.rdf.model.Resource;
 import jakarta.ws.rs.core.UriBuilder;
@@ -97,13 +99,16 @@ public URI getURIwithFormat() {
          * that do not affect the SPARQL select and view queries removed.
          */
         public URI getURIplain() {
-            URI x = UriBuilder.fromUri(URIUtils.changeFormatSuffix(requestURI, formatNames, ""))
-                    .replaceQueryParam(QueryParameter._FORMAT)
-                    .replaceQueryParam(QueryParameter._METADATA)
-                    .replaceQueryParam(QueryParameter._MARK)
-                    .replaceQueryParam(QueryParameter.callback)
-                    .build();
-            return x;
+            try {
+                return UriBuilder.fromUri(URIUtils.changeFormatSuffix(requestURI, formatNames, ""))
+                        .replaceQueryParam(QueryParameter._FORMAT)
+                        .replaceQueryParam(QueryParameter._METADATA)
+                        .replaceQueryParam(QueryParameter._MARK)
+                        .replaceQueryParam(QueryParameter.callback)
+                        .build();
+            } catch (UriBuilderException ube) {
+                throw new BadRequestException("The requested query string was invalid: " + requestURI.toString());
+            }
         }
     }
 
diff --git a/elda-lda/src/test/java/com/epimorphics/lda/core/APIEndpointRequestTest.java b/elda-lda/src/test/java/com/epimorphics/lda/core/APIEndpointRequestTest.java
new file mode 100644
index 000000000..8d5a643d4
--- /dev/null
+++ b/elda-lda/src/test/java/com/epimorphics/lda/core/APIEndpointRequestTest.java
@@ -0,0 +1,43 @@
+package com.epimorphics.lda.core;
+
+import com.epimorphics.lda.bindings.Bindings;
+import com.epimorphics.lda.support.Controls;
+import org.junit.Test;
+
+import java.net.URI;
+
+import static org.junit.Assert.*;
+
+public class APIEndpointRequestTest {
+    private final Controls c = new Controls();
+    private final Bindings b = new Bindings();
+
+    private APIEndpoint.Request request(String uri) {
+        URI requestUri = URI.create(uri);
+        return new APIEndpoint.Request(c, requestUri, b);
+    }
+
+    @Test
+    public void getUriPlain_withUnescapedQuery_returnsUri() {
+        URI result = request("http://localhost:8080/api/test?_view=all&thing.label=foo+&+bar").getURIplain();
+        assertEquals("http://localhost:8080/api/test?_view=all&+bar=&thing.label=foo+", result.toString());
+    }
+
+    @Test
+    public void getUriPlain_withViewParamsOnly_returnsUri() {
+        URI result = request("http://localhost:8080/api/test?_view=all&label=foo").getURIplain();
+        assertEquals("http://localhost:8080/api/test?_view=all&label=foo", result.toString());
+    }
+
+    @Test
+    public void getUriPlain_withNonViewParams_returnsPlainUri() {
+        URI result = request("http://localhost:8080/api/test?_metadata=true&_format=ttl&callback=hi&_view=all&label=foo&_mark=true").getURIplain();
+        assertEquals("http://localhost:8080/api/test?_view=all&label=foo", result.toString());
+    }
+
+    @Test
+    public void getUriPlain_withoutParams_returnsUri() {
+        URI result = request("http://localhost:8080/api/test").getURIplain();
+        assertEquals("http://localhost:8080/api/test", result.toString());
+    }
+}
\ No newline at end of file
diff --git a/elda-lda/src/test/java/com/epimorphics/lda/tests_support/MakeData.java b/elda-lda/src/test/java/com/epimorphics/lda/tests_support/MakeData.java
index a5ed19efd..c64e5b93b 100644
--- a/elda-lda/src/test/java/com/epimorphics/lda/tests_support/MakeData.java
+++ b/elda-lda/src/test/java/com/epimorphics/lda/tests_support/MakeData.java
@@ -22,6 +22,7 @@
 import org.apache.jena.vocabulary.RDF;
 import org.apache.jena.vocabulary.RDFS;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;
@@ -138,7 +139,11 @@ public static MultiMap<String, String> parseQueryString(String queryString) {
         for (int i = 0; i < pairs.length; i++) {
             if (pairs[i].isEmpty()) break;
             String[] pair = pairs[i].split("=");
-            result.add(pair[0], pair[1]);
+            if (pair.length > 1) {
+                result.add(pair[0], pair[1]);
+            } else {
+                result.add(pair[0], Collections.emptySet());
+            }
         }
         return result;
     }