diff --git a/docs/content/docs.md b/docs/content/docs.md
index 363302353..133284da7 100644
--- a/docs/content/docs.md
+++ b/docs/content/docs.md
@@ -227,9 +227,9 @@ fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid
 time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
 
 Options which use SIZE use kByte by default.  However, a suffix of `b`
-for bytes, `k` for kBytes, `M` for MBytes and `G` for GBytes may be
-used.  These are the binary units, eg 1, 2\*\*10, 2\*\*20, 2\*\*30
-respectively.
+for bytes, `k` for kBytes, `M` for MBytes, `G` for GBytes, `T` for
+TBytes and `P` for PBytes may be used.  These are the binary units, eg
+1, 2\*\*10, 2\*\*20, 2\*\*30 respectively.
 
 ### --backup-dir=DIR ###
 
diff --git a/fs/sizesuffix.go b/fs/sizesuffix.go
index 14652c3d5..adf2493fe 100644
--- a/fs/sizesuffix.go
+++ b/fs/sizesuffix.go
@@ -22,18 +22,24 @@ func (x SizeSuffix) string() (string, string) {
 		return "off", ""
 	case x == 0:
 		return "0", ""
-	case x < 1024:
+	case x < 1<<10:
 		scaled = float64(x)
 		suffix = ""
-	case x < 1024*1024:
-		scaled = float64(x) / 1024
+	case x < 1<<20:
+		scaled = float64(x) / (1 << 10)
 		suffix = "k"
-	case x < 1024*1024*1024:
-		scaled = float64(x) / 1024 / 1024
+	case x < 1<<30:
+		scaled = float64(x) / (1 << 20)
 		suffix = "M"
-	default:
-		scaled = float64(x) / 1024 / 1024 / 1024
+	case x < 1<<40:
+		scaled = float64(x) / (1 << 30)
 		suffix = "G"
+	case x < 1<<50:
+		scaled = float64(x) / (1 << 40)
+		suffix = "T"
+	default:
+		scaled = float64(x) / (1 << 50)
+		suffix = "P"
 	}
 	if math.Floor(scaled) == scaled {
 		return fmt.Sprintf("%.0f", scaled), suffix
@@ -80,6 +86,10 @@ func (x *SizeSuffix) Set(s string) error {
 		multiplier = 1 << 20
 	case 'g', 'G':
 		multiplier = 1 << 30
+	case 't', 'T':
+		multiplier = 1 << 40
+	case 'p', 'P':
+		multiplier = 1 << 50
 	default:
 		return errors.Errorf("bad suffix %q", suffix)
 	}
diff --git a/fs/sizesuffix_test.go b/fs/sizesuffix_test.go
index 45f8baa15..25529f997 100644
--- a/fs/sizesuffix_test.go
+++ b/fs/sizesuffix_test.go
@@ -44,6 +44,9 @@ func TestSizeSuffixUnit(t *testing.T) {
 		{1024 * 1024 * 1024, "1 GBytes"},
 		{10 * 1024 * 1024 * 1024, "10 GBytes"},
 		{10.1 * 1024 * 1024 * 1024, "10.100 GBytes"},
+		{10 * 1024 * 1024 * 1024 * 1024, "10 TBytes"},
+		{10 * 1024 * 1024 * 1024 * 1024 * 1024, "10 PBytes"},
+		{1 * 1024 * 1024 * 1024 * 1024 * 1024 * 1024, "1024 PBytes"},
 		{-1, "off"},
 		{-100, "off"},
 	} {
@@ -70,20 +73,22 @@ func TestSizeSuffixSet(t *testing.T) {
 		{"1M", 1024 * 1024, false},
 		{"1.g", 1024 * 1024 * 1024, false},
 		{"10G", 10 * 1024 * 1024 * 1024, false},
+		{"10T", 10 * 1024 * 1024 * 1024 * 1024, false},
+		{"10P", 10 * 1024 * 1024 * 1024 * 1024 * 1024, false},
 		{"off", -1, false},
 		{"OFF", -1, false},
 		{"", 0, true},
-		{"1p", 0, true},
-		{"1.p", 0, true},
-		{"1p", 0, true},
+		{"1q", 0, true},
+		{"1.q", 0, true},
+		{"1q", 0, true},
 		{"-1K", 0, true},
 	} {
 		ss := SizeSuffix(0)
 		err := ss.Set(test.in)
 		if test.err {
-			require.Error(t, err)
+			require.Error(t, err, test.in)
 		} else {
-			require.NoError(t, err)
+			require.NoError(t, err, test.in)
 		}
 		assert.Equal(t, test.want, int64(ss))
 	}