diff --git a/backend/union/policy/eplfs.go b/backend/union/policy/eplfs.go
index 454206b77..9b6107eb2 100644
--- a/backend/union/policy/eplfs.go
+++ b/backend/union/policy/eplfs.go
@@ -24,7 +24,8 @@ func (p *EpLfs) lfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
 	for _, u := range upstreams {
 		space, err := u.GetFreeSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
 		}
 		if space < minFreeSpace {
 			minFreeSpace = space
@@ -43,7 +44,8 @@ func (p *EpLfs) lfsEntries(entries []upstream.Entry) (upstream.Entry, error) {
 	for _, e := range entries {
 		space, err := e.UpstreamFs().GetFreeSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", e.UpstreamFs().Name())
 		}
 		if space < minFreeSpace {
 			minFreeSpace = space
diff --git a/backend/union/policy/eplus.go b/backend/union/policy/eplus.go
index e3aea8feb..ef8a963b0 100644
--- a/backend/union/policy/eplus.go
+++ b/backend/union/policy/eplus.go
@@ -24,7 +24,8 @@ func (p *EpLus) lus(upstreams []*upstream.Fs) (*upstream.Fs, error) {
 	for _, u := range upstreams {
 		space, err := u.GetUsedSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Used Space is not supported for upstream %s, treating as 0", u.Name())
 		}
 		if space < minUsedSpace {
 			minUsedSpace = space
@@ -43,7 +44,8 @@ func (p *EpLus) lusEntries(entries []upstream.Entry) (upstream.Entry, error) {
 	for _, e := range entries {
 		space, err := e.UpstreamFs().GetFreeSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Used Space is not supported for upstream %s, treating as 0", e.UpstreamFs().Name())
 		}
 		if space < minUsedSpace {
 			minUsedSpace = space
diff --git a/backend/union/policy/epmfs.go b/backend/union/policy/epmfs.go
index 06b195047..1370411c0 100644
--- a/backend/union/policy/epmfs.go
+++ b/backend/union/policy/epmfs.go
@@ -23,7 +23,8 @@ func (p *EpMfs) mfs(upstreams []*upstream.Fs) (*upstream.Fs, error) {
 	for _, u := range upstreams {
 		space, err := u.GetFreeSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", u.Name())
 		}
 		if maxFreeSpace < space {
 			maxFreeSpace = space
@@ -42,7 +43,8 @@ func (p *EpMfs) mfsEntries(entries []upstream.Entry) (upstream.Entry, error) {
 	for _, e := range entries {
 		space, err := e.UpstreamFs().GetFreeSpace()
 		if err != nil {
-			return nil, err
+			fs.LogPrintf(fs.LogLevelNotice, nil,
+				"Free Space is not supported for upstream %s, treating as infinite", e.UpstreamFs().Name())
 		}
 		if maxFreeSpace < space {
 			maxFreeSpace = space
diff --git a/backend/union/upstream/upstream.go b/backend/union/upstream/upstream.go
index 7543cfad0..07ec75661 100644
--- a/backend/union/upstream/upstream.go
+++ b/backend/union/upstream/upstream.go
@@ -3,6 +3,7 @@ package upstream
 import (
 	"context"
 	"io"
+	"math"
 	"path"
 	"path/filepath"
 	"strings"
@@ -254,13 +255,13 @@ func (f *Fs) GetFreeSpace() (int64, error) {
 	if atomic.LoadInt64(&f.cacheExpiry) <= time.Now().Unix() {
 		err := f.updateUsage()
 		if err != nil {
-			return 0, ErrUsageFieldNotSupported
+			return math.MaxInt64, ErrUsageFieldNotSupported
 		}
 	}
 	f.cacheMutex.RLock()
 	defer f.cacheMutex.RUnlock()
 	if f.usage.Free == nil {
-		return 0, ErrUsageFieldNotSupported
+		return math.MaxInt64, ErrUsageFieldNotSupported
 	}
 	return *f.usage.Free, nil
 }
diff --git a/docs/content/union.md b/docs/content/union.md
index 668969535..dac65134e 100644
--- a/docs/content/union.md
+++ b/docs/content/union.md
@@ -49,6 +49,18 @@ A path preserving policy will only consider upstreams where the relative path be
 
 When using non-path preserving policies paths will be created in target upstreams as necessary.
 
+#### Quota Relevant Policies
+
+Some policies rely on quota information. These policies should be used only if your upstreams support the respective quota fields.
+
+| Policy     | Required Field |
+|------------|----------------|
+| lfs, eplfs | Free           |
+| mfs, epmfs | Free           |
+| lus, eplus | Used           |
+
+To check if your upstream support the field, run `rclone about remote: [flags]` and see if the reuqired field exists.
+
 #### Filters
 
 Policies basically search upstream remotes and create a list of files / paths for functions to work on. The policy is responsible for filtering and sorting. The policy type defines the sorting but filtering is mostly uniform as described below.