diff --git a/userspace/lib/libterm/src/escape/csi.rs b/userspace/lib/libterm/src/escape/csi.rs
index fe209dad..a8c195f2 100644
--- a/userspace/lib/libterm/src/escape/csi.rs
+++ b/userspace/lib/libterm/src/escape/csi.rs
@@ -402,7 +402,7 @@ impl CsiState {
             (30..=37, _) => CharacterAttribute::FgIndex(Some(pm as u8 - 30)),
             (39, _) => CharacterAttribute::FgIndex(None),
             // Ps = 4 x ⇒ Set background color
-            (40..=47, _) => CharacterAttribute::BgIndex(Some(pm as u8 - 30)),
+            (40..=47, _) => CharacterAttribute::BgIndex(Some(pm as u8 - 40)),
             (49, _) => CharacterAttribute::BgIndex(None),
             // Ps = 9 x ⇒ Set foreground color
             (90..=97, _) => CharacterAttribute::FgIndex(Some(pm as u8 - 90)),