diff --git a/libmaxsi/heap.cpp b/libmaxsi/heap.cpp
index 5185f580..dc82e81d 100644
--- a/libmaxsi/heap.cpp
+++ b/libmaxsi/heap.cpp
@@ -229,7 +229,7 @@ namespace Maxsi
 		struct Chunk
 		{
 		public:
-			size_t size;
+			size_t size; // Includes size of Chunk and Trailer
 			union
 			{
 				size_t magic;
@@ -254,7 +254,7 @@ namespace Maxsi
 				size_t magic;
 				Chunk* prevunused;
 			};
-			size_t size;
+			size_t size; // Includes size of Chunk and Trailer
 
 		public:
 			bool IsUsed() { return magic == MAGIC; }
@@ -262,6 +262,8 @@ namespace Maxsi
 
 		};
 
+		const size_t OVERHEAD = sizeof(Chunk) + sizeof(Trailer);
+
 		// This is how a real chunk actually looks:
 		//struct RealChunk
 		//{
@@ -434,7 +436,7 @@ namespace Maxsi
 			ASSERT(ValidateHeap());
 			#endif
 
-			const size_t OVERHEAD = sizeof(Chunk) + sizeof(Trailer);
+			// The size field keeps both the allocation and meta information.
 			size += OVERHEAD;
 
 			// Round up to nearest alignment.
@@ -651,6 +653,22 @@ namespace Maxsi
 			Memory::Set(result, 0, total);
 			return result;
 		}
+
+		// TODO: Implement this function properly.
+		extern "C" void* realloc(void* ptr, size_t size)
+		{
+			if ( !ptr ) { return Allocate(size); }
+			Chunk* chunk = (Chunk*) ((addr_t) ptr - sizeof(Chunk));
+			ASSERT(chunk->IsUsed());
+			ASSERT(chunk->IsSane());
+			size_t allocsize = chunk->size - OVERHEAD;
+			if ( allocsize < size ) { return ptr; }
+			void* newptr = Allocate(size);
+			if ( !newptr ) { return NULL; }
+			Memory::Copy(newptr, ptr, allocsize);
+			Free(ptr);
+			return newptr;
+		}
 	}
 }
 
diff --git a/libmaxsi/include/stdlib.h b/libmaxsi/include/stdlib.h
index 0c972699..a65b7246 100644
--- a/libmaxsi/include/stdlib.h
+++ b/libmaxsi/include/stdlib.h
@@ -52,6 +52,7 @@ void _Exit(int status);
 void free(void*);
 void* malloc(size_t);
 int rand(void);
+void* realloc(void*, size_t);
 long strtol(const char* restrict, char** restrict, int);
 unsigned long strtoul(const char* restrict, char** restrict, int);
 unsigned long long strtoull(const char* restrict, char** restrict, int);
@@ -96,7 +97,6 @@ char* ptsname(int);
 int putenv(char*);
 void qsort(void*, size_t, size_t, int (*)(const void*, const void*));
 long random(void);
-void* realloc(void*, size_t);
 char* realpath(const char* restrict, char* restrict);
 unsigned short *seed48(unsigned short [3]);
 int setenv(const char*, const char*, int);