diff --git a/libs/ui/Region.cpp b/libs/ui/Region.cpp
index 224dc2c..55e3b99 100644
--- a/libs/ui/Region.cpp
+++ b/libs/ui/Region.cpp
@@ -22,7 +22,6 @@
 #include <android-base/stringprintf.h>
 
 #include <utils/Log.h>
-#include <utils/CallStack.h>
 
 #include <ui/Rect.h>
 #include <ui/Region.h>
@@ -31,10 +30,18 @@
 #include <private/ui/RegionHelper.h>
 
 // ----------------------------------------------------------------------------
-#define VALIDATE_REGIONS        (false)
+
+// ### VALIDATE_REGIONS ###
+// To enable VALIDATE_REGIONS traces, use the "libui-validate-regions-defaults"
+// in Android.bp. Do not #define VALIDATE_REGIONS here as it requires extra libs.
+
 #define VALIDATE_WITH_CORECG    (false)
 // ----------------------------------------------------------------------------
 
+#if defined(VALIDATE_REGIONS)
+#include <utils/CallStack.h>
+#endif
+
 #if VALIDATE_WITH_CORECG
 #include <core/SkRegion.h>
 #endif
@@ -67,7 +74,7 @@
 Region::Region(const Region& rhs)
     : mStorage(rhs.mStorage)
 {
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(rhs, "rhs copy-ctor");
 #endif
 }
@@ -203,7 +210,7 @@
             outputRegion.mStorage, direction_LTR);
     outputRegion.mStorage.add(r.getBounds()); // to make region valid, mStorage must end with bounds
 
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(outputRegion, "T-Junction free region");
 #endif
 
@@ -212,7 +219,7 @@
 
 Region& Region::operator = (const Region& rhs)
 {
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(*this, "this->operator=");
     validate(rhs, "rhs.operator=");
 #endif
@@ -599,10 +606,12 @@
         result = false;
         ALOGE_IF(!silent, "%s: mStorage size is 2, which is never valid", name);
     }
+#if defined(VALIDATE_REGIONS)
     if (result == false && !silent) {
         reg.dump(name);
         CallStack stack(LOG_TAG);
     }
+#endif
     return result;
 }
 
@@ -610,7 +619,7 @@
         const Region& lhs,
         const Region& rhs, int dx, int dy)
 {
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(lhs, "boolean_operation (before): lhs");
     validate(rhs, "boolean_operation (before): rhs");
     validate(dst, "boolean_operation (before): dst");
@@ -630,7 +639,7 @@
         operation(r);
     }
 
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(lhs, "boolean_operation: lhs");
     validate(rhs, "boolean_operation: rhs");
     validate(dst, "boolean_operation: dst");
@@ -728,7 +737,7 @@
         return;
     }
 
-#if VALIDATE_WITH_CORECG || VALIDATE_REGIONS
+#if VALIDATE_WITH_CORECG || defined(VALIDATE_REGIONS)
     boolean_operation(op, dst, lhs, Region(rhs), dx, dy);
 #else
     size_t lhs_count;
@@ -760,7 +769,7 @@
 void Region::translate(Region& reg, int dx, int dy)
 {
     if ((dx || dy) && !reg.isEmpty()) {
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
         validate(reg, "translate (before)");
 #endif
         size_t count = reg.mStorage.size();
@@ -770,7 +779,7 @@
             rects++;
             count--;
         }
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
         validate(reg, "translate (after)");
 #endif
     }
@@ -789,7 +798,7 @@
 }
 
 status_t Region::flatten(void* buffer, size_t size) const {
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(*this, "Region::flatten");
 #endif
     if (size < getFlattenedSize()) {
@@ -836,7 +845,7 @@
         result.mStorage.push_back(rect);
     }
 
-#if VALIDATE_REGIONS
+#if defined(VALIDATE_REGIONS)
     validate(result, "Region::unflatten");
 #endif