diff --git a/cdm-test-utils/src/main/resources/ucar/unidata/util/test/Dockerfile b/cdm-test-utils/src/main/resources/ucar/unidata/util/test/Dockerfile
index ed48604def..6b0b25cb00 100644
--- a/cdm-test-utils/src/main/resources/ucar/unidata/util/test/Dockerfile
+++ b/cdm-test-utils/src/main/resources/ucar/unidata/util/test/Dockerfile
@@ -6,7 +6,7 @@ USER root
 
 # TODO use release version of d4ts
 #ENV D4TS_WAR_URL https://artifacts.unidata.ucar.edu/repository/unidata-releases/edu/ucar/d4ts/5.4/d4ts-5.4.war
-ENV D4TS_WAR_URL https://artifacts.unidata.ucar.edu/repository/unidata-snapshots/edu/ucar/d4ts/5.5-SNAPSHOT/d4ts-5.5-20240507.221412-201.war
+ENV D4TS_WAR_URL https://artifacts.unidata.ucar.edu/repository/unidata-snapshots/edu/ucar/d4ts/5.5-SNAPSHOT/d4ts-5.5-20240603.195123-208.war
 ENV DTS_WAR_URL https://artifacts.unidata.ucar.edu/repository/unidata-releases/edu/ucar/dtswar/5.4/dtswar-5.4.war
 
 # Install necessary packages
diff --git a/cdm/core/src/main/java/thredds/filesystem/MFileOS.java b/cdm/core/src/main/java/thredds/filesystem/MFileOS.java
index 3bb3e7ff1a..094a02f6ec 100644
--- a/cdm/core/src/main/java/thredds/filesystem/MFileOS.java
+++ b/cdm/core/src/main/java/thredds/filesystem/MFileOS.java
@@ -88,9 +88,11 @@ public String getName() {
     return file.getName();
   }
 
+  @Nullable
   @Override
   public MFile getParent() {
-    return new MFileOS(file.getParentFile());
+    File parent = file.getParentFile();
+    return parent == null ? null : new MFileOS(parent);
   }
 
   @Override
diff --git a/cdm/core/src/main/java/ucar/nc2/filter/Classifier.java b/cdm/core/src/main/java/ucar/nc2/filter/Classifier.java
index 40842fa8b5..42fa157bd7 100644
--- a/cdm/core/src/main/java/ucar/nc2/filter/Classifier.java
+++ b/cdm/core/src/main/java/ucar/nc2/filter/Classifier.java
@@ -28,7 +28,6 @@ public static Classifier createFromVariable(VariableDS var) {
     }
   }
 
-
   public static Classifier emptyClassifier() {
     emptyClassifier = new Classifier();
     return emptyClassifier;
@@ -59,7 +58,6 @@ public int[] classifyWithAttributes(Array arr) {
     return classifiedArray;
   }
 
-
   /** Classify double array */
   public int[] classifyDoubleArray(Array arr) {
     int[] classifiedArray = new int[(int) arr.getSize()];
@@ -136,7 +134,4 @@ public static int[] stringToIntArray(String str) {
     return intArray;
   }
 
-
 }
-
-
diff --git a/cdm/core/src/test/java/ucar/nc2/ncml/TestEnhanceClassifier.java b/cdm/core/src/test/java/ucar/nc2/ncml/TestEnhanceClassifier.java
index c7b514fd5c..58acede18f 100644
--- a/cdm/core/src/test/java/ucar/nc2/ncml/TestEnhanceClassifier.java
+++ b/cdm/core/src/test/java/ucar/nc2/ncml/TestEnhanceClassifier.java
@@ -2,7 +2,6 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static ucar.ma2.MAMath.nearlyEquals;
-
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.List;
@@ -139,4 +138,5 @@ public void testEnhanceClassifier_classification() throws IOException {
     }
 
   }
+  
 }
diff --git a/cdm/core/src/test/java/ucar/nc2/util/TestURLnaming.java b/cdm/core/src/test/java/ucar/nc2/util/TestURLnaming.java
index a0f3771508..6444265fa2 100644
--- a/cdm/core/src/test/java/ucar/nc2/util/TestURLnaming.java
+++ b/cdm/core/src/test/java/ucar/nc2/util/TestURLnaming.java
@@ -5,6 +5,8 @@
 
 package ucar.nc2.util;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import java.lang.invoke.MethodHandles;
 import org.junit.Test;
 import org.slf4j.Logger;
@@ -30,6 +32,14 @@ public void testResolve() {
     testResolve("file://test/me/", "file:/wanna", "file:/wanna");
     testResolve("file://test/me/", "C:/wanna", "C:/wanna");
     testResolve("http://test/me/", "file:wanna", "file:wanna");
+
+    testResolve("urlWithoutSlash", "file:///path/with/slash", "file:///path/with/slash");
+  }
+
+  @Test
+  public void testResolveFile() {
+    assertThat(URLnaming.resolveFile("urlWithoutSlash", "file:///path/with/slash"))
+        .isEqualTo("file:///path/with/slash");
   }
 
   private void testResolve(String base, String rel, String result) {