diff --git a/pkg/reconciler/taskrun/taskrun.go b/pkg/reconciler/taskrun/taskrun.go
index 6da61b6f515..7c9e7dd573a 100644
--- a/pkg/reconciler/taskrun/taskrun.go
+++ b/pkg/reconciler/taskrun/taskrun.go
@@ -302,10 +302,12 @@ func (c *Reconciler) prepare(ctx context.Context, tr *v1beta1.TaskRun) (*v1beta1
 		return nil, nil, controller.NewPermanentError(err)
 	}
 
-	if err := validateWorkspaceCompatibilityWithAffinityAssistant(tr); err != nil {
-		logger.Errorf("TaskRun %q workspaces are invalid: %v", tr.Name, err)
-		tr.Status.MarkResourceFailed(podconvert.ReasonFailedValidation, err)
-		return nil, nil, controller.NewPermanentError(err)
+	if _, usesAssistant := tr.Annotations[workspace.AnnotationAffinityAssistantName]; usesAssistant {
+		if err := workspace.ValidateOnlyOnePVCIsUsed(tr.Spec.Workspaces); err != nil {
+			logger.Errorf("TaskRun %q workspaces incompatible with Affinity Assistant: %v", tr.Name, err)
+			tr.Status.MarkResourceFailed(podconvert.ReasonFailedValidation, err)
+			return nil, nil, controller.NewPermanentError(err)
+		}
 	}
 
 	// Initialize the cloud events if at least a CloudEventResource is defined
@@ -775,26 +777,3 @@ func storeTaskSpec(ctx context.Context, tr *v1beta1.TaskRun, ts *v1beta1.TaskSpe
 	}
 	return nil
 }
-
-// validateWorkspaceCompatibilityWithAffinityAssistant validates the TaskRun's compatibility
-// with the Affinity Assistant - if associated with an Affinity Assistant.
-// No more than one PVC-backed workspace can be used for a TaskRun that is associated with an
-// Affinity Assistant.
-func validateWorkspaceCompatibilityWithAffinityAssistant(tr *v1beta1.TaskRun) error {
-	_, isAssociatedWithAnAffinityAssistant := tr.Annotations[workspace.AnnotationAffinityAssistantName]
-	if !isAssociatedWithAnAffinityAssistant {
-		return nil
-	}
-
-	pvcWorkspaces := 0
-	for _, w := range tr.Spec.Workspaces {
-		if w.PersistentVolumeClaim != nil || w.VolumeClaimTemplate != nil {
-			pvcWorkspaces++
-		}
-	}
-
-	if pvcWorkspaces > 1 {
-		return fmt.Errorf("TaskRun mounts more than one PersistentVolumeClaim - that is forbidden when the Affinity Assistant is enabled")
-	}
-	return nil
-}
diff --git a/pkg/workspace/validate.go b/pkg/workspace/validate.go
index 2738b270b7d..18ba1535451 100644
--- a/pkg/workspace/validate.go
+++ b/pkg/workspace/validate.go
@@ -48,3 +48,25 @@ func ValidateBindings(w []v1beta1.WorkspaceDeclaration, wb []v1beta1.WorkspaceBi
 	}
 	return nil
 }
+
+// ValidateOnlyOnePVCIsUsed checks that a list of WorkspaceBinding uses only one
+// persistent volume claim.
+//
+// This is only useful to validate that WorkspaceBindings in TaskRuns are compatible
+// with affinity rules enforced by the AffinityAssistant.
+func ValidateOnlyOnePVCIsUsed(wb []v1beta1.WorkspaceBinding) error {
+	workspaceVolumes := make(map[string]bool)
+	for _, w := range wb {
+		if w.PersistentVolumeClaim != nil {
+			workspaceVolumes[w.PersistentVolumeClaim.ClaimName] = true
+		}
+		if w.VolumeClaimTemplate != nil {
+			workspaceVolumes[w.Name] = true
+		}
+	}
+
+	if len(workspaceVolumes) > 1 {
+		return fmt.Errorf("more than one PersistentVolumeClaim is bound")
+	}
+	return nil
+}
diff --git a/pkg/workspace/validate_test.go b/pkg/workspace/validate_test.go
index e79d104a509..7d115a93136 100644
--- a/pkg/workspace/validate_test.go
+++ b/pkg/workspace/validate_test.go
@@ -17,9 +17,11 @@ limitations under the License.
 package workspace
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1alpha1"
+	"github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1"
 	corev1 "k8s.io/api/core/v1"
 )
 
@@ -131,3 +133,89 @@ func TestValidateBindingsInvalid(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateOnlyOnePVCIsUsed_Valid(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		bindings []v1beta1.WorkspaceBinding
+	}{{
+		name:     "an error is not returned when no bindings are given",
+		bindings: []v1beta1.WorkspaceBinding{},
+	}, {
+		name: "an error is not returned when volume claims are not used",
+		bindings: []v1beta1.WorkspaceBinding{{
+			EmptyDir: &corev1.EmptyDirVolumeSource{},
+		}, {
+			Secret: &corev1.SecretVolumeSource{},
+		}},
+	}, {
+		name: "an error is not returned when one PV claim is used in two bindings",
+		bindings: []v1beta1.WorkspaceBinding{{
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}, {
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}},
+	}, {
+		name: "an error is not returned when one PV claim is used in two bindings with different subpaths",
+		bindings: []v1beta1.WorkspaceBinding{{
+			SubPath: "/pathA",
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}, {
+			SubPath: "/pathB",
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}},
+	}} {
+		t.Run(tc.name, func(t *testing.T) {
+			if err := ValidateOnlyOnePVCIsUsed(tc.bindings); err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+		})
+	}
+}
+
+func TestValidateOnlyOnePVCIsUsed_Invalid(t *testing.T) {
+	validationError := errors.New("more than one PersistentVolumeClaim is bound")
+	for _, tc := range []struct {
+		name     string
+		bindings []v1beta1.WorkspaceBinding
+		wantErr  error
+	}{{
+		name: "an error is returned when two different PV claims are used",
+		bindings: []v1beta1.WorkspaceBinding{{
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}, {
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "bar",
+			},
+		}},
+		wantErr: validationError,
+	}, {
+		name: "an error is returned when a PVC and volume claim template are mixed",
+		bindings: []v1beta1.WorkspaceBinding{{
+			PersistentVolumeClaim: &corev1.PersistentVolumeClaimVolumeSource{
+				ClaimName: "foo",
+			},
+		}, {
+			Name:                "bar",
+			VolumeClaimTemplate: &corev1.PersistentVolumeClaim{},
+		}},
+		wantErr: validationError,
+	}} {
+		t.Run(tc.name, func(t *testing.T) {
+			err := ValidateOnlyOnePVCIsUsed(tc.bindings)
+			if err == nil || (tc.wantErr.Error() != err.Error()) {
+				t.Errorf("expected %v received %v", tc.wantErr, err)
+			}
+		})
+	}
+}