diff --git a/conformance_tests.yaml b/conformance_tests.yaml
index 35ac083..aa2baf2 100644
--- a/conformance_tests.yaml
+++ b/conformance_tests.yaml
@@ -3313,3 +3313,18 @@
     Test that optional number output is returned as 0, not null
   tags: [ required, inline_javascript, command_line_tool ]
   id: 253
+
+- tool: tests/arg-empty-prefix-separate-false.cwl
+  job: tests/empty.json
+  output:
+    "out": {
+        "class": "File",
+        "checksum": "sha1$e1511352b3bd8c37082021bdc5c50ec8e0e3e8db",
+        "size": 17
+    }
+  label: argument_empty_prefix_separate_false
+  doc: |
+    Test that argument with empty string as prefix and separate 
+    false is not omitted from command line
+  tags: [ required, shell_command, command_line_tool ]
+  id: 254
diff --git a/tests/arg-empty-prefix-separate-false.cwl b/tests/arg-empty-prefix-separate-false.cwl
new file mode 100644
index 0000000..f3acf15
--- /dev/null
+++ b/tests/arg-empty-prefix-separate-false.cwl
@@ -0,0 +1,21 @@
+class: CommandLineTool
+cwlVersion: v1.1
+baseCommand: []
+inputs: []
+outputs: 
+  out:
+    type: File
+    outputBinding:
+      glob: out
+arguments:
+- position: 1
+  shellQuote: false
+  valueFrom: "non_existing_app"
+- position: 0
+  prefix: ''
+  separate: false
+  shellQuote: false
+  valueFrom: "echo"
+stdout: out
+requirements:
+- class: ShellCommandRequirement