diff --git a/libs/hwui/BakedOpRenderer.cpp b/libs/hwui/BakedOpRenderer.cpp
index 5f689b4..c147384 100644
--- a/libs/hwui/BakedOpRenderer.cpp
+++ b/libs/hwui/BakedOpRenderer.cpp
@@ -296,12 +296,9 @@
         }
     }
 
-    // dirty offscreenbuffer
-    if (dirtyBounds && mRenderTarget.offscreenBuffer) {
-        // register layer damage to draw-back region
-        android::Rect dirty(dirtyBounds->left, dirtyBounds->top,
-                dirtyBounds->right, dirtyBounds->bottom);
-        mRenderTarget.offscreenBuffer->region.orSelf(dirty);
+    if (dirtyBounds) {
+        // dirty offscreenbuffer if present
+        dirtyRenderTarget(*dirtyBounds);
     }
 }
 
@@ -329,29 +326,9 @@
     mRenderState.invokeFunctor(op.functor, DrawGlInfo::kModeDraw, &info);
 }
 
-#define VALIDATE_RECT_ARG(rect, arg) \
-        ((isnanf(rect.arg) || rect.arg < -10000 || rect.arg > 10000) ? (\
-            ALOGW("suspicious " #rect "." #arg "! %f", rect.arg),\
-            false) : true)
-
-#define VALIDATE_RECT(rect) \
-    VALIDATE_RECT_ARG(rect, bottom) & \
-    VALIDATE_RECT_ARG(rect, left) & \
-    VALIDATE_RECT_ARG(rect, top) & \
-    VALIDATE_RECT_ARG(rect, right)
-
 void BakedOpRenderer::dirtyRenderTarget(const Rect& uiDirty) {
     if (mRenderTarget.offscreenBuffer) {
-        bool valid = VALIDATE_RECT(uiDirty);
-        android::Rect dirty;
-        if (valid) {
-            dirty = android::Rect(uiDirty.left, uiDirty.top, uiDirty.right, uiDirty.bottom);
-        } else {
-            dirty = android::Rect(
-                    mRenderTarget.offscreenBuffer->viewportWidth,
-                    mRenderTarget.offscreenBuffer->viewportHeight);
-        }
-        mRenderTarget.offscreenBuffer->region.orSelf(dirty);
+        mRenderTarget.offscreenBuffer->dirty(uiDirty);
     }
 }
 
diff --git a/libs/hwui/renderstate/OffscreenBufferPool.cpp b/libs/hwui/renderstate/OffscreenBufferPool.cpp
index 54f38e8..5f984b5 100644
--- a/libs/hwui/renderstate/OffscreenBufferPool.cpp
+++ b/libs/hwui/renderstate/OffscreenBufferPool.cpp
@@ -54,6 +54,14 @@
     return Rect(0, viewportHeight * texY, viewportWidth * texX, 0);
 }
 
+void OffscreenBuffer::dirty(Rect dirtyArea) {
+    dirtyArea.doIntersect(0, 0, viewportWidth, viewportHeight);
+    if (!dirtyArea.isEmpty()) {
+        region.orSelf(android::Rect(dirtyArea.left, dirtyArea.top,
+                dirtyArea.right, dirtyArea.bottom));
+    }
+}
+
 void OffscreenBuffer::updateMeshFromRegion() {
     // avoid T-junctions as they cause artifacts in between the resultant
     // geometry when complex transforms occur.
diff --git a/libs/hwui/renderstate/OffscreenBufferPool.h b/libs/hwui/renderstate/OffscreenBufferPool.h
index 94155ef..089f131 100644
--- a/libs/hwui/renderstate/OffscreenBufferPool.h
+++ b/libs/hwui/renderstate/OffscreenBufferPool.h
@@ -48,6 +48,8 @@
 
     Rect getTextureCoordinates();
 
+    void dirty(Rect dirtyArea);
+
     // must be called prior to rendering, to construct/update vertex buffer
     void updateMeshFromRegion();
 
diff --git a/libs/hwui/tests/unit/OffscreenBufferPoolTests.cpp b/libs/hwui/tests/unit/OffscreenBufferPoolTests.cpp
index 2fd8795..0c6eb57 100644
--- a/libs/hwui/tests/unit/OffscreenBufferPoolTests.cpp
+++ b/libs/hwui/tests/unit/OffscreenBufferPoolTests.cpp
@@ -55,6 +55,14 @@
     });
 }
 
+TEST(OffscreenBuffer, dirty) {
+    TestUtils::runOnRenderThread([] (renderthread::RenderThread& thread) {
+        OffscreenBuffer buffer(thread.renderState(), Caches::getInstance(), 256u, 256u);
+        buffer.dirty(Rect(-100, -100, 100, 100));
+        EXPECT_EQ(android::Rect(100, 100), buffer.region.getBounds());
+    });
+}
+
 TEST(OffscreenBufferPool, construct) {
     TestUtils::runOnRenderThread([] (renderthread::RenderThread& thread) {
         OffscreenBufferPool pool;