diff --git a/Source/UI/CandidateUI/HorizontalCandidateController.swift b/Source/UI/CandidateUI/HorizontalCandidateController.swift
index a2e0785c..ab785d84 100644
--- a/Source/UI/CandidateUI/HorizontalCandidateController.swift
+++ b/Source/UI/CandidateUI/HorizontalCandidateController.swift
@@ -113,11 +113,7 @@ fileprivate class HorizontalCandidateView: NSView {
         NSColor.controlBackgroundColor.setFill() // Candidate list panel base background
         NSBezierPath.fill(bounds)
 
-        if #available(macOS 10.14, *) {
-            NSColor.separatorColor.setStroke()
-        } else {
-            NSColor.darkGray.setStroke()
-        }
+        NSColor.systemGray.withAlphaComponent(0.75).setStroke()
 
         NSBezierPath.strokeLine(from: NSPoint(x: bounds.size.width, y: 0.0), to: NSPoint(x: bounds.size.width, y: bounds.size.height))
 
diff --git a/Source/UI/CandidateUI/VerticalCandidateController.swift b/Source/UI/CandidateUI/VerticalCandidateController.swift
index 35055ba7..d5228159 100644
--- a/Source/UI/CandidateUI/VerticalCandidateController.swift
+++ b/Source/UI/CandidateUI/VerticalCandidateController.swift
@@ -119,11 +119,7 @@ fileprivate class VerticalCandidateView: NSView {
         NSColor.controlBackgroundColor.setFill() // Candidate list panel base background
         NSBezierPath.fill(bounds)
 
-        if #available(macOS 10.14, *) {
-            NSColor.separatorColor.setStroke()
-        } else {
-            NSColor.darkGray.setStroke()
-        }
+        NSColor.systemGray.withAlphaComponent(0.75).setStroke()
 
         NSBezierPath.strokeLine(from: NSPoint(x: bounds.size.width, y: 0.0), to: NSPoint(x: bounds.size.width, y: bounds.size.height))