diff --git a/samples/SimpleJNI/jni/Android.mk b/samples/SimpleJNI/jni/Android.mk
index ff0a6842d..1c2589fbf 100644
--- a/samples/SimpleJNI/jni/Android.mk
+++ b/samples/SimpleJNI/jni/Android.mk
@@ -41,8 +41,7 @@ LOCAL_STATIC_LIBRARIES :=
 LOCAL_C_INCLUDES += \
     $(JNI_H_INCLUDE)
 
-# No special compiler flags.
-LOCAL_CFLAGS +=
+LOCAL_CFLAGS := -Wall -Werror
 
 LOCAL_CXX_STL := none
 
diff --git a/samples/SimpleJNI/jni/native.cpp b/samples/SimpleJNI/jni/native.cpp
index 853c3d9cc..dd322c4f8 100644
--- a/samples/SimpleJNI/jni/native.cpp
+++ b/samples/SimpleJNI/jni/native.cpp
@@ -22,7 +22,7 @@
 #include "jni.h"
 
 static jint
-add(JNIEnv *env, jobject thiz, jint a, jint b) {
+add(JNIEnv* /*env*/, jobject /*thiz*/, jint a, jint b) {
 int result = a + b;
     ALOGI("%d + %d = %d", a, b, result);
     return result;
@@ -82,7 +82,7 @@ typedef union {
     void* venv;
 } UnionJNIEnvToVoid;
 
-jint JNI_OnLoad(JavaVM* vm, void* reserved)
+jint JNI_OnLoad(JavaVM* vm, void* /*reserved*/)
 {
     UnionJNIEnvToVoid uenv;
     uenv.venv = NULL;
diff --git a/tools/line_endings/line_endings.c b/tools/line_endings/line_endings.c
index 97e1a2913..5d3f8d263 100644
--- a/tools/line_endings/line_endings.c
+++ b/tools/line_endings/line_endings.c
@@ -88,7 +88,7 @@ main(int argc, char** argv)
                 len -= amt2;
             }
 
-            ftruncate(fd, 0);
+            (void)ftruncate(fd, 0);
             lseek(fd, 0, SEEK_SET);
             while (root) {
                 ssize_t amt2 = strlen(root->buf);
diff --git a/tutorials/MoarRam/jni/Android.mk b/tutorials/MoarRam/jni/Android.mk
index b1eec37a1..d2c9c387f 100644
--- a/tutorials/MoarRam/jni/Android.mk
+++ b/tutorials/MoarRam/jni/Android.mk
@@ -15,12 +15,15 @@
 
 LOCAL_PATH:= $(call my-dir)
 
+MoarRam_jni_cflags := -Wall -Werror -Wno-unused-parameter
+
 include $(CLEAR_VARS)
 
 LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE    := libmoarram-32
 LOCAL_SRC_FILES := foo.c
 LOCAL_SHARED_LIBRARIES += liblog
+LOCAL_CFLAGS := $(MoarRam_jni_cflags)
 
 include $(BUILD_SHARED_LIBRARY)
 
@@ -30,6 +33,7 @@ LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE    := libmoarram-2M
 LOCAL_SRC_FILES := bar.c
 LOCAL_SHARED_LIBRARIES += liblog
+LOCAL_CFLAGS := $(MoarRam_jni_cflags)
 
 include $(BUILD_SHARED_LIBRARY)
 
@@ -39,6 +43,7 @@ LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE    := libmoarram-17_71
 LOCAL_SRC_FILES := baz.c
 LOCAL_SHARED_LIBRARIES += liblog
+LOCAL_CFLAGS := $(MoarRam_jni_cflags)
 
 include $(BUILD_SHARED_LIBRARY)
 
@@ -48,5 +53,6 @@ LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE    := libmoarram-doublefree
 LOCAL_SRC_FILES := df.c
 LOCAL_SHARED_LIBRARIES += liblog
+LOCAL_CFLAGS := $(MoarRam_jni_cflags)
 
 include $(BUILD_SHARED_LIBRARY)