diff --git a/.appveyor.yml b/.appveyor.yml
index ae658cc3..68d7e69d 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -4,6 +4,7 @@ branches:
         - master
 skip_tags: true
 environment:
+    CFLAGS: /WX
     matrix:
         - BUILD_SHARED_LIBS: ON
         - BUILD_SHARED_LIBS: OFF
diff --git a/.travis.yml b/.travis.yml
index 72ac4bfe..eed58c7f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,8 +20,11 @@ addons:
             - libxcursor-dev
             - libxi-dev
 env:
-    - BUILD_SHARED_LIBS=ON
-    - BUILD_SHARED_LIBS=OFF
+    global:
+        - CFLAGS=-Werror
+    matrix:
+        - BUILD_SHARED_LIBS=ON
+        - BUILD_SHARED_LIBS=OFF
 script:
     - mkdir build
     - cd build