diff --git a/plugins/nf-quilt/src/main/nextflow/quilt/nio/QuiltPath.groovy b/plugins/nf-quilt/src/main/nextflow/quilt/nio/QuiltPath.groovy
index 91e94357..a1b94650 100644
--- a/plugins/nf-quilt/src/main/nextflow/quilt/nio/QuiltPath.groovy
+++ b/plugins/nf-quilt/src/main/nextflow/quilt/nio/QuiltPath.groovy
@@ -46,6 +46,10 @@ final class QuiltPath implements Path, Comparable {
     private final String[] paths
     private final boolean isFileName
 
+    static String joinOs(String... parts) {
+        return parts.join(FileSystems.getDefault().getSeparator())
+    }
+
     QuiltPath(QuiltFileSystem filesystem, QuiltParser parsed, boolean isFileName = false) {
         this.filesystem = filesystem
         this.parsed = parsed
@@ -215,15 +219,17 @@ final class QuiltPath implements Path, Comparable {
     Path relativize(Path other) {
         if (this == other) { return null }
         String file = (other in QuiltPath) ? ((QuiltPath)other).localPath() : other.toString()
-        String base = [pkg().toString(), parsed.getPath()].join(FileSystems.getDefault().getSeparator())
-        log.debug("relativize[$base] in [$file]")
+        String base = joinOs(pkg().toString(), parsed.getPath())
+        println("relativize[$base] in [$file]")
         int i = file.indexOf(base)
         if (i < 1) {
             throw new UnsupportedOperationException("other[$file] does not contain package[$base]")
         }
 
         String tail = file.substring(i + base.size())
-        if (tail.size() > 0 && tail[0] == '/') { tail = tail.substring(1) } // drop leading "/"
+        if (tail.size() > 0 && (tail[0] == '/' || tail[0] == '\\')) {
+            tail = tail.substring(1)
+        } // drop leading separator
         //log.debug("tail[$i] -> $tail")
         return Paths.get(tail)
     }
diff --git a/plugins/nf-quilt/src/test/nextflow/quilt/QuiltSpecification.groovy b/plugins/nf-quilt/src/test/nextflow/quilt/QuiltSpecification.groovy
index b38ab544..ba40aa7b 100644
--- a/plugins/nf-quilt/src/test/nextflow/quilt/QuiltSpecification.groovy
+++ b/plugins/nf-quilt/src/test/nextflow/quilt/QuiltSpecification.groovy
@@ -23,6 +23,7 @@ import nextflow.quilt.jep.QuiltPackage
 import java.nio.ByteBuffer
 import java.nio.channels.SeekableByteChannel
 import java.nio.file.FileSystem
+import java.nio.file.FileSystems
 import java.nio.file.Files
 import java.nio.file.Paths
 import java.nio.file.Path
@@ -51,6 +52,10 @@ class QuiltSpecification extends Specification {
         return 'quilt+s3://udp-spec#package=nf-quilt/source'
     }
 
+    static String OsConvert(String path) {
+        return path.replace('/', FileSystems.getDefault().getSeparator())
+    }
+
     @Shared String testURI
 
     @Shared String pluginsMode
diff --git a/plugins/nf-quilt/src/test/nextflow/quilt/nio/QuiltNioTest.groovy b/plugins/nf-quilt/src/test/nextflow/quilt/nio/QuiltNioTest.groovy
index 0303b252..823f3329 100644
--- a/plugins/nf-quilt/src/test/nextflow/quilt/nio/QuiltNioTest.groovy
+++ b/plugins/nf-quilt/src/test/nextflow/quilt/nio/QuiltNioTest.groovy
@@ -565,8 +565,8 @@ class QuiltNioTest extends QuiltSpecification {
         dirs.size() == 4
         dirs.contains('null')
         dirs.contains('foo')
-        dirs.contains('foo/bar')
-        dirs.contains('foo/bar/baz')
+        dirs.contains(OsConvert('foo/bar'))
+        dirs.contains(OsConvert('foo/bar/baz'))
 
         when:
         dirs = []
@@ -657,8 +657,8 @@ class QuiltNioTest extends QuiltSpecification {
         dirs.contains('foo')
         files.size() == 3
         files.containsKey('foo')
-        files.containsKey('foo/bar')
-        files.containsKey('foo/baz')
+        files.containsKey(OsConvert('foo/bar'))
+        files.containsKey(OsConvert('foo/baz'))
     }
 
     void 'should handle file names with same prefix'() {