diff -r bb8b75c6bfdf Python/ceval.c
--- a/Python/ceval.c	Wed Dec 09 11:27:34 2015 +0200
+++ b/Python/ceval.c	Wed Dec 09 11:46:52 2015 +0200
@@ -892,7 +892,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
     TARGET_##op: \
         opcode = op; \
         if (HAS_ARG(op)) \
-            oparg = NEXTARG(); \
+            NEXTARG(oparg); \
     case op: \
         goto impl; \
 
@@ -900,7 +900,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
     TARGET_##op: \
         opcode = op; \
         if (HAS_ARG(op)) \
-            oparg = NEXTARG(); \
+            NEXTARG(oparg); \
     case op:
 
 
@@ -996,8 +996,33 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
 
 #define INSTR_OFFSET()  ((int)(next_instr - first_instr))
 #define NEXTOP()        (*next_instr++)
-#define NEXTARG()       (next_instr += 2, (next_instr[-1]<<8) + next_instr[-2])
-#define PEEKARG()       ((next_instr[2]<<8) + next_instr[1])
+#if PY_LITTLE_ENDIAN
+#  define NEXTARG(oparg)  do {                  \
+        union {                                 \
+            unsigned short value;               \
+            unsigned char bytes[2];             \
+        } u;                                    \
+        memcpy(&u.bytes, next_instr, 2);        \
+        (oparg) = (int)u.value;                 \
+        next_instr += 2;                        \
+    } while(0)
+#  define PEEKARG(oparg)  do {                  \
+        union {                                 \
+            unsigned short value;               \
+            unsigned char bytes[2];             \
+        } u;                                    \
+        memcpy(&u.bytes, next_instr + 1, 2);    \
+        (oparg) = (int)u.value;                 \
+    } while(0)
+#else
+#  define PEEKARG(oparg)  do {                          \
+        (oparg) = (next_instr[2]<<8) + next_instr[1];   \
+    } while(0)
+#  define NEXTARG(oparg)  do {                          \
+        (oparg) = (next_instr[1]<<8) + next_instr[0];   \
+        next_instr += 2;                                \
+    } while(0)
+#endif
 #define JUMPTO(x)       (next_instr = first_instr + (x))
 #define JUMPBY(x)       (next_instr += (x))
 
@@ -1035,7 +1060,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
 #else
 #define PREDICT(op)             if (*next_instr == op) goto PRED_##op
 #define PREDICTED(op)           PRED_##op: next_instr++
-#define PREDICTED_WITH_ARG(op)  PRED_##op: oparg = PEEKARG(); next_instr += 3
+#define PREDICTED_WITH_ARG(op)  PRED_##op: PEEKARG(oparg); next_instr += 3
 #endif
 
 
@@ -1326,7 +1351,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
         oparg = 0;   /* allows oparg to be stored in a register because
             it doesn't have to be remembered across a full loop */
         if (HAS_ARG(opcode))
-            oparg = NEXTARG();
+            NEXTARG(oparg);
     dispatch_opcode:
 #ifdef DYNAMIC_EXECUTION_PROFILE
 #ifdef DXPAIRS
@@ -3432,8 +3457,10 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
         }
 
         TARGET(EXTENDED_ARG) {
+            int oparg2;
             opcode = NEXTOP();
-            oparg = oparg<<16 | NEXTARG();
+            NEXTARG(oparg2);
+            oparg = oparg<<16 | oparg2;
             goto dispatch_opcode;
         }
 
@@ -5287,8 +5314,9 @@ unicode_concatenate(PyObject *v, PyObjec
         switch (*next_instr) {
         case STORE_FAST:
         {
-            int oparg = PEEKARG();
             PyObject **fastlocals = f->f_localsplus;
+            int oparg;
+            PEEKARG(oparg);
             if (GETLOCAL(oparg) == v)
                 SETLOCAL(oparg, NULL);
             break;
@@ -5297,7 +5325,10 @@ unicode_concatenate(PyObject *v, PyObjec
         {
             PyObject **freevars = (f->f_localsplus +
                                    f->f_code->co_nlocals);
-            PyObject *c = freevars[PEEKARG()];
+            PyObject *c;
+            int oparg;
+            PEEKARG(oparg);
+            c = freevars[oparg];
             if (PyCell_GET(c) == v)
                 PyCell_Set(c, NULL);
             break;
@@ -5305,8 +5336,11 @@ unicode_concatenate(PyObject *v, PyObjec
         case STORE_NAME:
         {
             PyObject *names = f->f_code->co_names;
-            PyObject *name = GETITEM(names, PEEKARG());
+            PyObject *name;
             PyObject *locals = f->f_locals;
+            int oparg;
+            PEEKARG(oparg);
+            name = GETITEM(names, oparg);
             if (PyDict_CheckExact(locals) &&
                 PyDict_GetItem(locals, name) == v) {
                 if (PyDict_DelItem(locals, name) != 0) {