diff --git a/cwltool/schemas/draft-3/Workflow.yml b/cwltool/schemas/draft-3/Workflow.yml
index 4c36dfa08..bdd8559b6 100644
--- a/cwltool/schemas/draft-3/Workflow.yml
+++ b/cwltool/schemas/draft-3/Workflow.yml
@@ -2,6 +2,7 @@ $base: "https://w3id.org/cwl/cwl#"
 
 $namespaces:
   cwl: "https://w3id.org/cwl/cwl#"
+  rdfs: "http://www.w3.org/2000/01/rdf-schema#"
 
 $graph:
 
diff --git a/cwltool/schemas/v1.0/Process.yml b/cwltool/schemas/v1.0/Process.yml
index 37b203871..419d4d19a 100644
--- a/cwltool/schemas/v1.0/Process.yml
+++ b/cwltool/schemas/v1.0/Process.yml
@@ -3,6 +3,7 @@ $base: "https://w3id.org/cwl/cwl#"
 $namespaces:
   cwl: "https://w3id.org/cwl/cwl#"
   sld: "https://w3id.org/cwl/salad#"
+  rdfs: "http://www.w3.org/2000/01/rdf-schema#"
 
 $graph:
 
diff --git a/cwltool/schemas/v1.0/Workflow.yml b/cwltool/schemas/v1.0/Workflow.yml
index 26bde8e29..387b25cba 100644
--- a/cwltool/schemas/v1.0/Workflow.yml
+++ b/cwltool/schemas/v1.0/Workflow.yml
@@ -2,6 +2,7 @@ $base: "https://w3id.org/cwl/cwl#"
 
 $namespaces:
   cwl: "https://w3id.org/cwl/cwl#"
+  rdfs: "http://www.w3.org/2000/01/rdf-schema#"
 
 $graph:
 
diff --git a/cwltool/schemas/v1.1.0-dev1/Process.yml b/cwltool/schemas/v1.1.0-dev1/Process.yml
index cf8e03aed..0746fa499 100644
--- a/cwltool/schemas/v1.1.0-dev1/Process.yml
+++ b/cwltool/schemas/v1.1.0-dev1/Process.yml
@@ -3,6 +3,7 @@ $base: "https://w3id.org/cwl/cwl#"
 $namespaces:
   cwl: "https://w3id.org/cwl/cwl#"
   sld: "https://w3id.org/cwl/salad#"
+  rdfs: "http://www.w3.org/2000/01/rdf-schema#"
 
 $graph:
 
diff --git a/cwltool/schemas/v1.1.0-dev1/Workflow.yml b/cwltool/schemas/v1.1.0-dev1/Workflow.yml
index 3f2f9c150..979e17388 100644
--- a/cwltool/schemas/v1.1.0-dev1/Workflow.yml
+++ b/cwltool/schemas/v1.1.0-dev1/Workflow.yml
@@ -2,6 +2,7 @@ $base: "https://w3id.org/cwl/cwl#"
 
 $namespaces:
   cwl: "https://w3id.org/cwl/cwl#"
+  rdfs: "http://www.w3.org/2000/01/rdf-schema#
 
 $graph: