diff --git a/.appveyor.yml b/.appveyor.yml
index 2ad8f641e426..f27fa78fb89c 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -5,6 +5,12 @@ platform: x64
 configuration:  # a trick to construct a build matrix with multiple Python versions
   - 3.7
 
+# only build pull requests and
+# commits to 'master'
+branches:
+  only:
+    - master
+
 environment:
   matrix:
     - COMPILER: MINGW