diff -urN psyco-dist.old/c/codegen.c psyco-dist.new/c/codegen.c
--- psyco-dist.old/c/codegen.c	2006-04-17 04:34:34.000000000 -0500
+++ psyco-dist.new/c/codegen.c	2007-11-15 16:36:01.000000000 -0600
@@ -308,7 +308,12 @@
 #endif
                     }
                 }
+				#ifdef __APPLE__
+				/* Adjust # of arguments for MacOS 16-byte stack alignment */
+                result = psyco_call_var(c_function, (count+3)&~3, args);
+				#else
                 result = psyco_call_var(c_function, count, args);
+				#endif
                 if (PyErr_Occurred()) {
                     if (has_refs)
                         for (i = 0; i < count; i++) 
@@ -387,6 +392,7 @@
 	stackbase = po->stack_depth;
 	po->stack_depth += totalstackspace;
 	STACK_CORRECTION(totalstackspace);
+	CALL_STACK_ALIGN(count);
 	for (i=count; i--; ) {
 		switch (argtags[i]) {
 			
@@ -467,6 +473,7 @@
 				}
                         }
 	}
+
 	return NULL;
 }
 
diff -urN psyco-dist.old/c/i386/iencoding.c psyco-dist.new/c/i386/iencoding.c
--- psyco-dist.old/c/i386/iencoding.c	2006-02-15 08:04:12.000000000 -0600
+++ psyco-dist.new/c/i386/iencoding.c	2007-11-15 16:36:01.000000000 -0600
@@ -48,12 +48,17 @@
   code_t* code = po->code;
   void* result;
   code_t* fixvalue;
+  #ifdef __APPLE__
+  int aligndelta;
+  #endif
 
   if (restore)
     TEMP_SAVE_REGS_FN_CALLS;
   else
     SAVE_REGS_FN_CALLS(true);
 
+  CALL_STACK_ALIGN_DELTA(1+(extraarg != SOURCE_DUMMY), aligndelta);
+  
   /* first pushed argument */
   if (extraarg != SOURCE_DUMMY)
     CALL_SET_ARG_FROM_RT(extraarg, 1, 2);  /* argument index 1 out of total 2 */
@@ -79,6 +84,7 @@
                       4*nb_args,  /*           4*nb_args  */
                       0);         /* not used             */
       code += 3;
+	  CALL_STACK_ALIGN_RESTORE(aligndelta);
       TEMP_RESTORE_REGS_FN_CALLS_AND_JUMP;
     }
   else
@@ -109,10 +115,25 @@
 	int i, initial_depth;
 	Source* p;
 	bool ccflags;
+	#ifdef __APPLE__
+	int aligncount=0;
+	#endif
 	BEGIN_CODE
 	/* cannot use NEED_CC(): it might clobber one of the registers
 	   mentioned in argsources */
         ccflags = HAS_CCREG(po);
+    #ifdef __APPLE__
+	/* Calculate number of registers that will be pushed by
+	   NEED_REGISTER */
+	for (i=0; i<REG_TOTAL; i++)
+	{
+		vinfo_t* _content = REG_NUMBER(po, i);
+		if (_content != NULL)
+			if (RUNTIME_STACK(_content) == RUNTIME_STACK_NONE)
+				aligncount++;
+	}
+	#endif
+	CALL_STACK_ALIGN(1+(ccflags!=0)+aligncount);
 	if (ccflags)
 		PUSH_CC_FLAGS();
 	for (i=0; i<REG_TOTAL; i++)
diff -urN psyco-dist.old/c/i386/iencoding.h psyco-dist.new/c/i386/iencoding.h
--- psyco-dist.old/c/i386/iencoding.h	2006-02-13 18:21:38.000000000 -0600
+++ psyco-dist.new/c/i386/iencoding.h	2007-11-15 16:36:01.000000000 -0600
@@ -20,8 +20,13 @@
     (a quite minor overhead). Set to 0 to disable. No effect on real
     optimizations. */
 #ifndef COMPACT_ENCODING
+#ifdef __APPLE__
+/* COMPACT_ENCODING not yet supported on MacOS X */
+# define COMPACT_ENCODING   0
+#else
 # define COMPACT_ENCODING   1
 #endif
+#endif
 
 /* Define to 0 to use EBP as any other register, or to 1 to reserve it */
 #ifndef EBP_IS_RESERVED
@@ -652,6 +657,31 @@
   JUMP_TO((code_t*)(target));                                           \
 } while (0)
 
+#ifdef __APPLE__
+/* Stack alignment for MacOS X IA-32 ABI */
+#define CALL_STACK_ALIGN_DELTA(nbargs, delta) do { \
+    int sp = po->stack_depth-INITIAL_STACK_DEPTH+(nbargs)*4;	\
+	delta = ((sp+15)&~15)-sp; \
+	po->stack_depth += delta; \
+	STACK_CORRECTION(delta); \
+} while (0)
+
+#define CALL_STACK_ALIGN(nbargs) do { \
+	int delta; \
+    CALL_STACK_ALIGN_DELTA(nbargs, delta); \
+} while (0)
+
+#define CALL_STACK_ALIGN_RESTORE(delta) do { \
+	po->stack_depth -= delta; \
+	STACK_CORRECTION(-delta); \
+} while (0)
+#else
+/* Dummy stack alignment for non-MacOS X */
+#define CALL_STACK_ALIGN_DELTA(nbargs, delta)
+#define CALL_STACK_ALIGN(nbargs)
+#define CALL_STACK_ALIGN_RESTORE(delta)
+#endif
+	
 /* load the 'dst' register with the run-time address of 'source'
    which must be in the stack */
 #define LOAD_ADDRESS_FROM_RT(source, dst)    do {                               \
diff -urN psyco-dist.old/c/i386/iprocessor.c psyco-dist.new/c/i386/iprocessor.c
--- psyco-dist.old/c/i386/iprocessor.c	2006-11-26 07:03:26.000000000 -0600
+++ psyco-dist.new/c/i386/iprocessor.c	2007-11-15 16:36:01.000000000 -0600
@@ -21,6 +21,10 @@
   PUSH_REG_INSTR(REG_386_ESI),  /*   PUSH ESI        */
   PUSH_REG_INSTR(REG_386_EDI),  /*   PUSH EDI        */
   0x8B, 0x5C, 0x24, 32,         /*   MOV EBX, [ESP+32] (finfo frame stack ptr) */
+#ifdef __APPLE__
+  /* Align stack on 16-byte boundary for MacOS X */
+  0x83, 0xEC, 8,                /*   SUB ESP, 8      */
+#endif
   0x6A, -1,                     /*   PUSH -1         */
   0x89, 0x23,                   /*   MOV [EBX], ESP  */
   0xEB, +5,                     /*   JMP Label2      */
@@ -31,6 +35,10 @@
   0x39, 0xCA,                   /*   CMP EDX, ECX    */
   0x75, -9,                     /*   JNE Label1      */
   0xFF, 0xD0,                   /*   CALL *EAX     (callee removes args)  */
+#ifdef __APPLE__
+  /* Restore stack from 16-byte alignment on MacOS X */
+  0x83, 0xC4, 8,                /*   ADD ESP, 8      */
+#endif
   POP_REG_INSTR(REG_386_EDI),   /*   POP EDI         */
   POP_REG_INSTR(REG_386_ESI),   /*   POP ESI         */
   POP_REG_INSTR(REG_386_EBX),   /*   POP EBX         */
@@ -67,9 +75,18 @@
 	0x53,			/*   PUSH EBX                      */
 	0x8B, 0x5C, 0x24, 12,	/*   MOV EBX, [ESP+12]  (argcount) */
 	0x8B, 0x44, 0x24, 8,	/*   MOV EAX, [ESP+8]   (c_func)   */
+#ifdef __APPLE__
+    /* Align stack on 16-byte boundary for MacOS X */
+    0x83, 0xEC, 8,                /*   SUB ESP, 8      */
+#endif
 	0x09, 0xDB,		/*   OR EBX, EBX                   */
 	0x74, +16,		/*   JZ Label1                     */
+#ifdef __APPLE__
+	/* Arguments are 8 bytes further up stack on MacOS X */
+	0x8B, 0x54, 0x24, 24,	/*   MOV EDX, [ESP+24] (arguments) */
+#else
 	0x8B, 0x54, 0x24, 16,	/*   MOV EDX, [ESP+16] (arguments) */
+#endif
 	0x8D, 0x0C, 0x9A,	/*   LEA ECX, [EDX+4*EBX]          */
 				/* Label2:                         */
 	0x83, 0xE9, 4,		/*   SUB ECX, 4                    */
@@ -78,6 +95,10 @@
 	0x75, -9,		/*   JNE Label2                    */
 				/* Label1:                         */
 	0xFF, 0xD0,		/*   CALL *EAX                     */
+#ifdef __APPLE__
+    /* Restore stack from 16-byte alignment on MacOS X */
+    0x83, 0xC4, 8,                /*   ADD ESP, 8      */
+#endif
 	0x8D, 0x24, 0x9C,	/*   LEA ESP, [ESP+4*EBX]          */
 	0x5B,			/*   POP EBX                       */
 	0xC3,			/*   RET                           */
diff -urN psyco-dist.old/c/ivm/iencoding.h psyco-dist.new/c/ivm/iencoding.h
--- psyco-dist.old/c/ivm/iencoding.h	2006-02-13 18:21:38.000000000 -0600
+++ psyco-dist.new/c/ivm/iencoding.h	2007-11-15 16:36:01.000000000 -0600
@@ -248,6 +248,10 @@
   else if (_stackcorr > 0)                              \
     INSN_pushn(_stackcorr / sizeof(long));              \
 } while (0)
+/* Dummy stack alignment for non-MacOS X */
+#define CALL_STACK_ALIGN_DELTA(nbargs, delta)
+#define CALL_STACK_ALIGN(nbargs)
+#define CALL_STACK_ALIGN_RESTORE(delta)
 
 #define FUNCTION_RET(popbytes)      do {                                        \
   INSN_ret((popbytes) / sizeof(long) + 1);   /* +1 for the retaddr itself */    \