diff --git a/devstack/lib/ironic b/devstack/lib/ironic
index 72d6c36dbe..0585a4049c 100644
--- a/devstack/lib/ironic
+++ b/devstack/lib/ironic
@@ -3516,12 +3516,19 @@ function downgrade_dnsmasq {
     # NOTE(TheJulia): The intent here is to use dnsmasq version
     # which does not crash on segfaults or sigabort when configuration
     # is updated. See https://bugs.launchpad.net/ironic/+bug/2026757
-    sudo dpkg -r dnsmasq-base
-    git clone http://thekelleys.org.uk/git/dnsmasq.git -b v2.85 --depth 1
-    pushd dnsmasq
-    sed -i 's|^PREFIX.*|PREFIX = /usr|' Makefile
-    sudo make install
-    popd
+    if dnsmasq --version | grep -q "Dnsmasq version 2.85"; then
+        # NOTE(JayF) Keep Ironic devstack plugin idempotent by skipping
+        # downgrade if we already have the desired version.
+        echo "Dnsmasq already downgraded, continuing..."
+    else
+        echo "Downgrading dnsmasq..."
+        sudo dpkg -r dnsmasq-base
+        git clone http://thekelleys.org.uk/git/dnsmasq.git -b v2.85 --depth 1
+        pushd dnsmasq
+        sed -i 's|^PREFIX.*|PREFIX = /usr|' Makefile
+        sudo make install
+        popd
+    fi
 }
 
 # Restore xtrace + pipefail