diff --git a/libs/ui/Region.cpp b/libs/ui/Region.cpp
index 1994f6a..a060a5f 100644
--- a/libs/ui/Region.cpp
+++ b/libs/ui/Region.cpp
@@ -56,6 +56,9 @@
 Region::Region(const Region& rhs)
     : mBounds(rhs.mBounds), mStorage(rhs.mStorage)
 {
+#if VALIDATE_REGIONS
+    validate(rhs, "rhs copy-ctor");
+#endif
 }
 
 Region::Region(const Rect& rhs)
@@ -76,7 +79,8 @@
 Region& Region::operator = (const Region& rhs)
 {
 #if VALIDATE_REGIONS
-    validate(rhs, "operator=");
+    validate(*this, "this->operator=");
+    validate(rhs, "rhs.operator=");
 #endif
     mBounds = rhs.mBounds;
     mStorage = rhs.mStorage;
@@ -366,6 +370,12 @@
         const Region& lhs,
         const Region& rhs, int dx, int dy)
 {
+#if VALIDATE_REGIONS
+    validate(lhs, "boolean_operation (before): lhs");
+    validate(rhs, "boolean_operation (before): rhs");
+    validate(dst, "boolean_operation (before): dst");
+#endif
+
     size_t lhs_count;
     Rect const * const lhs_rects = lhs.getArray(&lhs_count);