diff --git a/install.sh b/install.sh
index 588e874..a08f55c 100755
--- a/install.sh
+++ b/install.sh
@@ -47,9 +47,23 @@ chmod +x "$S"
 # Install SNS
 if [ ! -r "/bin/sns" ]; then
   sudo cp "$S" "/bin/sns"
+else
+    if [ -r "/bin/sns" ]; then
+        if grep "simple note system" "/bin/sns"; then
+            sudo rm /bin/sns
+            sudo cp "$S" "/bin/sns"
+        fi
+    fi
 fi
 # Install Bash completion
 if [ ! -r "/usr/share/bash-completion/completions/sns" ]; then
    sudo cp "src/bash-completion/sns" "/usr/share/bash-completion/completions/sns"
+else
+    if [ -r "/usr/share/bash-completion/completions/sns" ]; then
+        if grep "simple note system" "/usr/share/bash-completion/completions/sns"; then
+            sudo rm /bin/sns
+            sudo cp "$S" "/bin/sns"
+        fi
+    fi
 fi
 exit