diff --git a/src/vs/base/browser/ui/segmentedIconToggle/segmentedIconToggle.css b/src/vs/base/browser/ui/segmentedIconToggle/segmentedIconToggle.css
index 18bd6e3958833..49049d8caddf5 100644
--- a/src/vs/base/browser/ui/segmentedIconToggle/segmentedIconToggle.css
+++ b/src/vs/base/browser/ui/segmentedIconToggle/segmentedIconToggle.css
@@ -81,6 +81,13 @@
 	width: var(--segmented-icon-toggle-single-width, 54px);
 }
 
+/* With only one icon present there is no segment to divide, so the housing border
+ * reads as an out-of-place box around a lone button. Hide it (keeping the border
+ * box so the width stays stable) to match the other borderless input controls. */
+.monaco-segmented-icon-toggle-container.single .monaco-segmented-icon-toggle {
+	border-color: transparent;
+}
+
 /* Absent cells collapse to zero width (icons slide into place as the housing recenters).
  * `visibility: hidden` (delayed until the width/opacity transition finishes) also removes
  * the collapsed native button from the Tab order and accessibility tree, so it can't be