diff --git a/common/include/u_mem.h b/common/include/u_mem.h
index cf15a7a31..71ef9b022 100644
--- a/common/include/u_mem.h
+++ b/common/include/u_mem.h
@@ -29,6 +29,13 @@ COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
 
 #define MEM_K 1.5	// Dynamic array growth factor
 
+#ifdef DEBUG_BIAS_MEMORY_ALLOCATIONS
+#include "compiler-array.h"
+#define DXX_DEBUG_BIAS_MEMORY_ALLOCATION (sizeof(array<double, 2>))
+#else
+#define DXX_DEBUG_BIAS_MEMORY_ALLOCATION (0)
+#endif
+
 #ifdef DEBUG_MEMORY_ALLOCATIONS
 void mem_init(void);
 
@@ -50,10 +57,32 @@ void mem_validate_heap();
 
 #else
 
-#define mem_malloc(size,var,file,line)	((void)var,(void)file,(void)line,malloc((size)))
-#define mem_calloc(nmemb,size,var,file,line)	((void)var,(void)file,(void)line,calloc((nmemb),(size)))
-#define mem_realloc(ptr,size,var,file,line)	((void)var,(void)file,(void)line,realloc((ptr),(size)))
-#define mem_free	free
+#ifdef DEBUG_BIAS_MEMORY_ALLOCATIONS
+#define bias_malloc(SIZE)	({	\
+		auto p = malloc((SIZE) + DXX_DEBUG_BIAS_MEMORY_ALLOCATION);	\
+		p ? p + DXX_DEBUG_BIAS_MEMORY_ALLOCATION : p;	\
+	})
+/* Bias calloc wastes a bit extra to keep the math simple */
+#define bias_calloc(NMEMB,SIZE)	({	\
+		auto p = calloc((NMEMB), (SIZE) + DXX_DEBUG_BIAS_MEMORY_ALLOCATION);	\
+		p ? p + DXX_DEBUG_BIAS_MEMORY_ALLOCATION : p;	\
+	})
+#define bias_realloc(PTR,SIZE)	({	\
+		auto p = realloc(reinterpret_cast<char *>(PTR) - DXX_DEBUG_BIAS_MEMORY_ALLOCATION, (SIZE) + DXX_DEBUG_BIAS_MEMORY_ALLOCATION);	\
+		p ? p + DXX_DEBUG_BIAS_MEMORY_ALLOCATION : p;	\
+	})
+#define bias_free(PTR)	free(reinterpret_cast<char *>(PTR) - DXX_DEBUG_BIAS_MEMORY_ALLOCATION)
+#else
+#define bias_malloc	malloc
+#define bias_calloc calloc
+#define bias_realloc realloc
+#define bias_free free
+#endif
+
+#define mem_malloc(size,var,file,line)	((void)var,(void)file,(void)line,bias_malloc((size)))
+#define mem_calloc(nmemb,size,var,file,line)	((void)var,(void)file,(void)line,bias_calloc((nmemb),(size)))
+#define mem_realloc(ptr,size,var,file,line)	((void)var,(void)file,(void)line,bias_realloc((ptr),(size)))
+#define mem_free	bias_free
 
 static inline void mem_init(void)
 {
@@ -75,7 +104,6 @@ T *CALLOC(T *&r, std::size_t count, const char *var, const char *file, unsigned
 }
 
 #define d_malloc(size)      mem_malloc((size),"Unknown", __FILE__,__LINE__ )
-#define d_calloc(nmemb,size)    mem_calloc((nmemb),(size),"Unknown", __FILE__,__LINE__ )
 #define d_realloc(ptr,size) mem_realloc((ptr),(size),"Unknown", __FILE__,__LINE__ )
 template <typename T>
 static inline void d_free(T *&ptr)
diff --git a/similar/mem/mem.cpp b/similar/mem/mem.cpp
index 666414086..10fb38e9b 100644
--- a/similar/mem/mem.cpp
+++ b/similar/mem/mem.cpp
@@ -57,10 +57,8 @@ static int free_list[MAX_INDEX];
 static int num_blocks = 0;
 
 static int Initialized = 0;
-
 static int LargestIndex = 0;
-
-int out_of_memory = 0;
+static int out_of_memory = 0;
 
 void mem_init()
 {
@@ -130,8 +128,7 @@ void *mem_malloc(size_t size, const char * var, const char * filename, unsigned
 		//con_printf(CON_CRITICAL, "\tBlock '%s' created in %s, line %d.", Varname[id], Filename[id], LineNum[id] );
 		Error( "MEM_OUT_OF_SLOTS" );
 	}
-
-	ptr = malloc( size+CHECKSIZE );
+	ptr = malloc(size + DXX_DEBUG_BIAS_MEMORY_ALLOCATION + CHECKSIZE);
 
 	if (ptr==NULL)
 	{
@@ -140,7 +137,7 @@ void *mem_malloc(size_t size, const char * var, const char * filename, unsigned
 		con_printf(CON_CRITICAL, "\tBlock '%s' created in %s, line %d.", Varname[id], Filename[id], LineNum[id] );
 		Error( "MEM_OUT_OF_MEMORY" );
 	}
-
+	ptr = reinterpret_cast<char *>(ptr) + DXX_DEBUG_BIAS_MEMORY_ALLOCATION;
 	MallocBase[id] = ptr;
 	MallocSize[id] = size;
 	Varname[id] = var;
@@ -238,7 +235,6 @@ void mem_free( void * buffer )
 		Int3();
 		return;
 	}
-
 	id = mem_find_id( buffer );
 
 	if (id==-1 &&  (!out_of_memory))
@@ -253,6 +249,7 @@ void mem_free( void * buffer )
 	
 	BytesMalloced -= MallocSize[id];
 
+	buffer = reinterpret_cast<char *>(buffer) - DXX_DEBUG_BIAS_MEMORY_ALLOCATION;
 	free( buffer );
 
 	Present[id] = 0;
@@ -344,9 +341,6 @@ static unsigned int SmallestAddress = 0xFFFFFFF;
 static unsigned int LargestAddress = 0x0;
 static unsigned int BytesMalloced = 0;
 
-#define CHECKSIZE 16
-#define CHECKBYTE 0xFC
-
 void mem_init()
 {
 	Initialized = 1;