diff --git a/Source/UI/CandidateUI/HorizontalCandidateController.swift b/Source/UI/CandidateUI/HorizontalCandidateController.swift
index c120d8eb..a2e0785c 100644
--- a/Source/UI/CandidateUI/HorizontalCandidateController.swift
+++ b/Source/UI/CandidateUI/HorizontalCandidateController.swift
@@ -105,7 +105,9 @@ fileprivate class HorizontalCandidateView: NSView {
         self.wantsLayer = true
         self.layer?.borderColor = NSColor.selectedMenuItemTextColor.withAlphaComponent(0.30).cgColor
         self.layer?.borderWidth = 1.0
-        self.layer?.cornerRadius = 6.0
+        if #available(macOS 10.13, *) {
+            self.layer?.cornerRadius = 6.0
+        }
         
         let bounds = self.bounds
         NSColor.controlBackgroundColor.setFill() // Candidate list panel base background
diff --git a/Source/UI/CandidateUI/VerticalCandidateController.swift b/Source/UI/CandidateUI/VerticalCandidateController.swift
index 69bf624b..35055ba7 100644
--- a/Source/UI/CandidateUI/VerticalCandidateController.swift
+++ b/Source/UI/CandidateUI/VerticalCandidateController.swift
@@ -111,7 +111,9 @@ fileprivate class VerticalCandidateView: NSView {
         self.wantsLayer = true
         self.layer?.borderColor = NSColor.selectedMenuItemTextColor.withAlphaComponent(0.30).cgColor
         self.layer?.borderWidth = 1.0
-        self.layer?.cornerRadius = 6.0
+        if #available(macOS 10.13, *) {
+            self.layer?.cornerRadius = 6.0
+        }
         
         let bounds = self.bounds
         NSColor.controlBackgroundColor.setFill() // Candidate list panel base background