diff --git a/src/common/hacks.cpp b/src/common/hacks.cpp
index 7e03508fe..57b52efd5 100644
--- a/src/common/hacks.cpp
+++ b/src/common/hacks.cpp
@@ -41,7 +41,7 @@ static const char *mosu_hacks[] = {
   ENGAGE_ALLOW_AVC_IN_VFW_MODE,
   ENGAGE_KEEP_BITSTREAM_AR_INFO,
   ENGAGE_USE_SIMPLE_BLOCK,
-  ENGAGE_OLD_AAC_CODECID,
+  ENGAGE_NEW_AAC_CODECID,
   NULL
 };
 static vector<string> engaged_hacks;
diff --git a/src/common/hacks.h b/src/common/hacks.h
index 84814600c..96bac708d 100644
--- a/src/common/hacks.h
+++ b/src/common/hacks.h
@@ -38,7 +38,7 @@ using namespace std;
 #define ENGAGE_ALLOW_AVC_IN_VFW_MODE "allow_avc_in_vfw_mode"
 #define ENGAGE_KEEP_BITSTREAM_AR_INFO "keep_bitstream_ar_info"
 #define ENGAGE_USE_SIMPLE_BLOCK "use_simpleblock"
-#define ENGAGE_OLD_AAC_CODECID "old_aac_codecid"
+#define ENGAGE_NEW_AAC_CODECID "new_aac_codecid"
 
 void MTX_DLL_API engage_hacks(const string &hacks);
 bool MTX_DLL_API hack_engaged(const string &hack);
diff --git a/src/mmg/mmg.cpp b/src/mmg/mmg.cpp
index 2bc0dcee2..a856d4eba 100644
--- a/src/mmg/mmg.cpp
+++ b/src/mmg/mmg.cpp
@@ -136,9 +136,9 @@ wxString cli_options[][2] = {
         "mode, e.g. when it is read from an AVI") },
   { wxT("--engage use_simpleblock"),
     wxT("Enable use of SimpleBlock instead of BlockGroup when possible.") },
-  { wxT("--engage old_aac_codecid"),
-    wxT("Use the old AAC codec IDs (e.g. 'A_AAC/MPEG4/SBR') instead of the "
-        "new one ('A_AAC').") },
+  { wxT("--engage new_aac_codecid"),
+    wxT("Use the new AAC codec ID ('A_AAC') instead of the "
+        "old ones (e.g. 'A_AAC/MPEG4/SBR').") },
   { wxT("--engage cow"),
     wxT("No help available.") },
   { wxT(""), wxT("") }
diff --git a/src/output/p_aac.cpp b/src/output/p_aac.cpp
index 2dd2efe6e..36764056e 100644
--- a/src/output/p_aac.cpp
+++ b/src/output/p_aac.cpp
@@ -120,7 +120,7 @@ aac_packetizer_c::get_aac_packet(unsigned long *header,
 
 void
 aac_packetizer_c::set_headers() {
-  if (!hack_engaged(ENGAGE_OLD_AAC_CODECID))
+  if (hack_engaged(ENGAGE_NEW_AAC_CODECID))
     set_codec_id(MKV_A_AAC);
   else if (id == AAC_ID_MPEG4) {
     if (profile == AAC_PROFILE_MAIN)
@@ -152,7 +152,7 @@ aac_packetizer_c::set_headers() {
 
   if ((ti.private_data != NULL) && (ti.private_size > 0))
     set_codec_private(ti.private_data, ti.private_size);
-  else if (!hack_engaged(ENGAGE_OLD_AAC_CODECID)) {
+  else if (hack_engaged(ENGAGE_NEW_AAC_CODECID)) {
     unsigned char buffer[5];
     int length;
 
diff --git a/tests/results.txt b/tests/results.txt
index ae154b074..d035a7520 100644
--- a/tests/results.txt
+++ b/tests/results.txt
@@ -1,7 +1,7 @@
 T_001mp3:36cd12fade1091a83a585e91ae5ba688:passed:20040825-175700
-T_002aac:54dfa564896e33a7de03f84d7fef9326:passed:20040825-175700
+T_002aac:3d8cbfb08d21492b91cb71a0ae0c35bd:passed:20040825-175700
 T_003ac3:e9643247b6e39a5860797c8f69ba0767:passed:20040825-175700
-T_004aacmp4:54dfa564896e33a7de03f84d7fef9326:passed:20040825-175700
+T_004aacmp4:508bee3abb5804438929e20faeae1fd7:passed:20040825-175700
 T_005flac:3cf801306ecfcb92fcda003478e3b57a:passed:20040825-175700
 T_006oggflac:93cac873d232626d6cccd564c882e85e:passed:20040825-175700
 T_007oggvorbis:89670229d8a89da9f5f8f924e475e6de:passed:20040825-175700
@@ -17,14 +17,14 @@ T_016cuesheet:b548f8c5b9f53a1a78f97aab6e30214c:passed:20040825-175700
 T_017chapters:585d4d598649022d55d1bb4fc182e116-1b3baf61b14a84b1c67882c1e7cd8458:passed:20040825-175700
 T_018attachments:ac6394cde92a4b8e14bd5dc52008abb1-e7df2fcf5c909aac898c826ca8a3ba00:passed:20040825-175700
 T_019attachments2:adba3d9cbc2db44108d029bd30973906-2172092cf50ed209f4497e66c99bf94f-adba3d9cbc2db44108d029bd30973906-6414e28248ebcc96865a16120d3b43f6:passed:20040825-175700
-T_020languages:186c2f094be2dcc5fea0539d153c88e3:passed:20040825-234208
+T_020languages:ba2fc0db66309659d76a2f9e00cdb32a:passed:20040825-234208
 T_021aspect_ratio:969b6644cd0fd5c95149506433a6c820-c9a746671d466b8bd08d649315e588e2:passed:20040825-234244
 T_022display_dimensions:6d00ed374f16ac37746c6e6e35adfedd:passed:20040825-234339
-T_023no_x:3d20c3d3d539993fb1fc0f2998446e46-d2c893b7469160f7e56ea8acaf03a2a6-512bd182f04693109d70b43310176169:passed:20040825-234343
+T_023no_x:3d20c3d3d539993fb1fc0f2998446e46-633a860a77ec0bc421f5ffede3886f80-4543f8c2e1b44d60916ca5679c78f44d:passed:20040825-234343
 T_024sync_mp3:93bf6f0a02a5022c48ea4adacb64d8f1-843be89680a77d167f65f89c7c7122a8:passed:20040825-234344
 T_025sync_vorbis:b673f0144c40cbf99ee9589096004ba8-87954bb9b6db0c8e4142bac48a84bf83:passed:20040825-234344
 T_026sync_pcm:ba603463fdae736629a83fd6e787459c-df52679a140b3f2aebd591a19c617d37:passed:20040825-234346
-T_027default_track:59ba079b777775b9b6a1094506e2d959:passed:20040825-234348
+T_027default_track:7d6d04092901127898f3da79ff339c82:passed:20040825-234348
 T_028compression:9ddf5346ffb58c5297ef297035dbccab:passed:20040825-234348
 T_029link:all ok:passed:20040825-235039
 T_032cues:310accca0b5867df9d9f3d403995c006:passed:20040825-235040
@@ -47,7 +47,7 @@ T_048X_chapters_ogmstyle:5ecb42d20d78b4f73fc2340a2e4f0803:passed:20040920-192349
 T_049ass:b50e8bc1d9acbe0a5a940e18e4b33cde:passed:20040929-113852
 T_050X_ass:6aeb4aef55511282630e9f0e69777c46-d65638e96a393b01deb6d5e132d35552:passed:20040929-113852
 T_200mp2_from_mp4:4f856114687cb1682c0a28fec925ea73:passed:20040917-185156
-T_201avc_from_mp4_with_par:3c3b46cf77b8bc67317e451d4b4bd435:passed:20050125-224528
+T_201avc_from_mp4_with_par:bcf892f063800c7167a828e91f9e0b3c:passed:20050125-224528
 T_202avc_from_mp4_with_par_bframes:fcb4d77c4136d033a3df044234c9b299:passed:20050125-224635
 T_203wavpack_with_correctiondata:a375abc2174544fda652ec9ea0bffd61:passed:20050201-094411
 T_204wavpack_without_correctiondata:58e1c78c7a26d67af71845754519c652:passed:20050201-094414