diff --git a/tci.c b/tci.c
index 7cbb39ed4b..82705fe772 100644
--- a/tci.c
+++ b/tci.c
@@ -1,7 +1,7 @@
 /*
  * Tiny Code Interpreter for QEMU
  *
- * Copyright (c) 2009, 2011 Stefan Weil
+ * Copyright (c) 2009, 2011, 2016 Stefan Weil
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -19,9 +19,12 @@
 
 #include "qemu/osdep.h"
 
-/* Defining NDEBUG disables assertions (which makes the code faster). */
-#if !defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG)
-# define NDEBUG
+/* Enable TCI assertions only when debugging TCG (and without NDEBUG defined).
+ * Without assertions, the interpreter runs much faster. */
+#if defined(CONFIG_DEBUG_TCG)
+# define tci_assert(cond) assert(cond)
+#else
+# define tci_assert(cond) ((void)0)
 #endif
 
 #include "qemu-common.h"
@@ -56,7 +59,7 @@ static tcg_target_ulong tci_reg[TCG_TARGET_NB_REGS];
 
 static tcg_target_ulong tci_read_reg(TCGReg index)
 {
-    assert(index < ARRAY_SIZE(tci_reg));
+    tci_assert(index < ARRAY_SIZE(tci_reg));
     return tci_reg[index];
 }
 
@@ -105,9 +108,9 @@ static uint64_t tci_read_reg64(TCGReg index)
 
 static void tci_write_reg(TCGReg index, tcg_target_ulong value)
 {
-    assert(index < ARRAY_SIZE(tci_reg));
-    assert(index != TCG_AREG0);
-    assert(index != TCG_REG_CALL_STACK);
+    tci_assert(index < ARRAY_SIZE(tci_reg));
+    tci_assert(index != TCG_AREG0);
+    tci_assert(index != TCG_REG_CALL_STACK);
     tci_reg[index] = value;
 }
 
@@ -325,7 +328,7 @@ static uint64_t tci_read_ri64(uint8_t **tb_ptr)
 static tcg_target_ulong tci_read_label(uint8_t **tb_ptr)
 {
     tcg_target_ulong label = tci_read_i(tb_ptr);
-    assert(label != 0);
+    tci_assert(label != 0);
     return label;
 }
 
@@ -468,11 +471,11 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
 
     tci_reg[TCG_AREG0] = (tcg_target_ulong)env;
     tci_reg[TCG_REG_CALL_STACK] = sp_value;
-    assert(tb_ptr);
+    tci_assert(tb_ptr);
 
     for (;;) {
         TCGOpcode opc = tb_ptr[0];
-#if !defined(NDEBUG)
+#if defined(CONFIG_DEBUG_TCG) && !defined(NDEBUG)
         uint8_t op_size = tb_ptr[1];
         uint8_t *old_code_ptr = tb_ptr;
 #endif
@@ -525,7 +528,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             break;
         case INDEX_op_br:
             label = tci_read_label(&tb_ptr);
-            assert(tb_ptr == old_code_ptr + op_size);
+            tci_assert(tb_ptr == old_code_ptr + op_size);
             tb_ptr = (uint8_t *)label;
             continue;
         case INDEX_op_setcond_i32:
@@ -600,7 +603,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             t0 = tci_read_r32(&tb_ptr);
             t1 = tci_read_r(&tb_ptr);
             t2 = tci_read_s32(&tb_ptr);
-            assert(t1 != sp_value || (int32_t)t2 < 0);
+            tci_assert(t1 != sp_value || (int32_t)t2 < 0);
             *(uint32_t *)(t1 + t2) = t0;
             break;
 
@@ -725,7 +728,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             condition = *tb_ptr++;
             label = tci_read_label(&tb_ptr);
             if (tci_compare32(t0, t1, condition)) {
-                assert(tb_ptr == old_code_ptr + op_size);
+                tci_assert(tb_ptr == old_code_ptr + op_size);
                 tb_ptr = (uint8_t *)label;
                 continue;
             }
@@ -751,7 +754,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             condition = *tb_ptr++;
             label = tci_read_label(&tb_ptr);
             if (tci_compare64(tmp64, v64, condition)) {
-                assert(tb_ptr == old_code_ptr + op_size);
+                tci_assert(tb_ptr == old_code_ptr + op_size);
                 tb_ptr = (uint8_t *)label;
                 continue;
             }
@@ -885,7 +888,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             t0 = tci_read_r64(&tb_ptr);
             t1 = tci_read_r(&tb_ptr);
             t2 = tci_read_s32(&tb_ptr);
-            assert(t1 != sp_value || (int32_t)t2 < 0);
+            tci_assert(t1 != sp_value || (int32_t)t2 < 0);
             *(uint64_t *)(t1 + t2) = t0;
             break;
 
@@ -992,7 +995,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             condition = *tb_ptr++;
             label = tci_read_label(&tb_ptr);
             if (tci_compare64(t0, t1, condition)) {
-                assert(tb_ptr == old_code_ptr + op_size);
+                tci_assert(tb_ptr == old_code_ptr + op_size);
                 tb_ptr = (uint8_t *)label;
                 continue;
             }
@@ -1087,7 +1090,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             break;
         case INDEX_op_goto_tb:
             t0 = tci_read_i32(&tb_ptr);
-            assert(tb_ptr == old_code_ptr + op_size);
+            tci_assert(tb_ptr == old_code_ptr + op_size);
             tb_ptr += (int32_t)t0;
             continue;
         case INDEX_op_qemu_ld_i32:
@@ -1234,7 +1237,7 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             TODO();
             break;
         }
-        assert(tb_ptr == old_code_ptr + op_size);
+        tci_assert(tb_ptr == old_code_ptr + op_size);
     }
 exit:
     return next_tb;