diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 555b323..d446cf8 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -10,8 +10,17 @@ on:
       - 'Cargo.lock'
       - 'bundler.toml'
       - 'tools/**'
+  # Mirrors the push filter. Without it a PR touching only the README would run a
+  # full build - the branch filter alone constrains where, not what.
   pull_request:
     branches: [ master ]
+    paths:
+      - 'src/**'
+      - 'xtask/**'
+      - 'Cargo.toml'
+      - 'Cargo.lock'
+      - 'bundler.toml'
+      - 'tools/**'
   workflow_dispatch:
 
 # Target the self-hosted Rust/audio runner registered to the `musiikki` org.