diff --git a/include/binder/MemoryHeapBase.h b/include/binder/MemoryHeapBase.h
index bbbda9c16..ea9b66c49 100644
--- a/include/binder/MemoryHeapBase.h
+++ b/include/binder/MemoryHeapBase.h
@@ -58,10 +58,13 @@ public:
 
     /* implement IMemoryHeap interface */
     virtual int         getHeapID() const;
+
+    /* virtual address of the heap. returns MAP_FAILED in case of error */
     virtual void*       getBase() const;
+
     virtual size_t      getSize() const;
     virtual uint32_t    getFlags() const;
-    virtual uint32_t      getOffset() const;
+    virtual uint32_t    getOffset() const;
 
     const char*         getDevice() const;
 
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 6ed9843f4..ceae8d789 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -2497,7 +2497,7 @@ status_t SurfaceFlinger::captureScreenImplLocked(const sp<IBinder>& display,
             sp<MemoryHeapBase> base(
                     new MemoryHeapBase(size, 0, "screen-capture") );
             void* const ptr = base->getBase();
-            if (ptr) {
+            if (ptr != MAP_FAILED) {
                 // capture the screen with glReadPixels()
                 ScopedTrace _t(ATRACE_TAG, "glReadPixels");
                 glReadPixels(0, 0, sw, sh, GL_RGBA, GL_UNSIGNED_BYTE, ptr);