diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d2d7709..019c83f 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -1,6 +1,10 @@
 name: Build
 
-on: [push]
+on:
+  push:
+  pull_request:
+    types:
+      - synchronize
 
 env:
   # Path to the solution file relative to the root of the project.
@@ -46,11 +50,11 @@ jobs:
 
       - name: Build (Linux)
         if: startsWith(matrix.os, 'ubuntu')
-        run: cd linux && make
+        run: cd linux && make CDEFS="-Werror"
 
       - name: Build (Mac)
         if: startsWith(matrix.os, 'mac')
-        run: cd mac && make
+        run: cd mac && make CDEFS="-Werror"
 
       # - name: Restore NuGet packages
       #   working-directory: ${{env.GITHUB_WORKSPACE}}
diff --git a/linux/Makefile b/linux/Makefile
index 714c336..37ca21b 100644
--- a/linux/Makefile
+++ b/linux/Makefile
@@ -3,7 +3,8 @@ all: libwooting-rgb-sdk.so
 prefix ?= /usr/local
 
 CC ?= gcc
-CFLAGS ?= -Wall -g -fPIC
+CDEFS=
+CFLAGS ?= -Wall -g -fPIC ${CDEFS}
 CPPFLAGS ?= #-DDEBUG_LOG
 LDFLAGS ?= -Wall -g -Wl,--no-as-needed
 
diff --git a/mac/Makefile b/mac/Makefile
index 0750f42..edb8984 100644
--- a/mac/Makefile
+++ b/mac/Makefile
@@ -3,7 +3,8 @@ all: libwooting-rgb-sdk.dylib
 prefix ?= /usr/local
 
 CC ?= gcc
-CFLAGS ?= -Wall -g -fPIC
+CDEFS=
+CFLAGS ?= -Wall -g -fPIC ${CDEFS}
 CPPFLAGS ?= #-DDEBUG_LOG
 LDFLAGS ?= -Wall -g