diff --git a/headers/private/kernel/util/SimpleAllocator.h b/headers/private/kernel/util/SimpleAllocator.h
index df2a5be6ac..1221c56974 100644
--- a/headers/private/kernel/util/SimpleAllocator.h
+++ b/headers/private/kernel/util/SimpleAllocator.h
@@ -266,6 +266,9 @@ public:
 #ifdef DEBUG_MAX_HEAP_USAGE
 		fMaxHeapUsage = std::max(fMaxHeapUsage, fMaxHeapSize - fAvailable);
 #endif
+#ifdef DEBUG_ALLOCATIONS
+		memset(allocated, 0xcc, chunk->Size());
+#endif
 
 		return allocated;
 	}
@@ -306,7 +309,7 @@ public:
 
 		FreeChunk* freedChunk = FreeChunk::SetToAllocated(allocated);
 
-#ifdef DEBUG_ALLOCATIONS
+#ifdef DEBUG_VALIDATE_HEAP_ON_FREE
 		if (freedChunk->Size() > (fMaxHeapSize - fAvailable)) {
 			panic("freed chunk %p clobbered (%#zx)!\n", freedChunk,
 				freedChunk->Size());
@@ -321,6 +324,10 @@ public:
 			}
 		}
 #endif
+#ifdef DEBUG_ALLOCATIONS
+		for (uint32 i = 0; i < (freedChunk->Size() / 4); i++)
+			((uint32*)allocated)[i] = 0xdeadbeef;
+#endif
 
 		// try to join the new free chunk with an existing one
 		// it may be joined with up to two chunks
diff --git a/src/system/boot/loader/heap.cpp b/src/system/boot/loader/heap.cpp
index 9fbd1e8436..043be1395e 100644
--- a/src/system/boot/loader/heap.cpp
+++ b/src/system/boot/loader/heap.cpp
@@ -16,11 +16,16 @@
 #include <util/OpenHashTable.h>
 
 
+#if KDEBUG
 #define DEBUG_ALLOCATIONS
-	// if defined, freed memory is filled with 0xcc
+	// if defined, allocated memory is filled with 0xcc and freed memory with 0xdeadbeef
 #define DEBUG_MAX_HEAP_USAGE
 	// if defined, the maximum heap usage is determined and printed before
 	// entering the kernel
+#define DEBUG_VALIDATE_HEAP_ON_FREE
+	// if defined, the heap integrity is checked on every free
+	// (must have DEBUG_MAX_HEAP_USAGE defined also)
+#endif
 
 #include <util/SimpleAllocator.h>