diff --git a/lib_enc/ivas_mct_core_enc.c b/lib_enc/ivas_mct_core_enc.c
index 48a7abc42f48ce40c9d1804b2551036cd98474a0..40153a3c69be115415439e11d2e3783fb5541ef5 100755
--- a/lib_enc/ivas_mct_core_enc.c
+++ b/lib_enc/ivas_mct_core_enc.c
@@ -334,8 +334,7 @@ void ivas_mct_core_enc(
 
     for ( ch = 0; ch < nChannels; ch++ )
     {
-        if (
-            sts[ch]->mct_chan_mode == MCT_CHAN_MODE_IGNORE )
+        if ( sts[ch]->mct_chan_mode == MCT_CHAN_MODE_IGNORE )
         {
             continue;
         }
@@ -359,16 +358,21 @@ void ivas_mct_core_enc(
             }
             else
             {
-                /* power spectrum: MDCT^2 + MDST^2 */
-                powerSpecMsInv[ch][n][0] = inv_spectrum[ch][n][0] * inv_spectrum[ch][n][0];
-
-                for ( i = 1; i < L_subframeTCX - 1; i++ )
+#ifdef FIX_483b
+                if ( hMCT->currBlockDataCnt > 0 )
+#endif
                 {
-                    mdst = ( inv_spectrum[ch][n][i + 1] - inv_spectrum[ch][n][i - 1] ); /* An MDST estimate */
-                    powerSpecMsInv[ch][n][i] = mdst * mdst + inv_spectrum[ch][n][i] * inv_spectrum[ch][n][i];
-                }
+                    /* power spectrum: MDCT^2 + MDST^2 */
+                    powerSpecMsInv[ch][n][0] = inv_spectrum[ch][n][0] * inv_spectrum[ch][n][0];
+
+                    for ( i = 1; i < L_subframeTCX - 1; i++ )
+                    {
+                        mdst = ( inv_spectrum[ch][n][i + 1] - inv_spectrum[ch][n][i - 1] ); /* An MDST estimate */
+                        powerSpecMsInv[ch][n][i] = mdst * mdst + inv_spectrum[ch][n][i] * inv_spectrum[ch][n][i];
+                    }
 
-                powerSpecMsInv[ch][n][L_subframeTCX - 1] = inv_spectrum[ch][n][L_subframeTCX - 1] * inv_spectrum[ch][n][L_subframeTCX - 1];
+                    powerSpecMsInv[ch][n][L_subframeTCX - 1] = inv_spectrum[ch][n][L_subframeTCX - 1] * inv_spectrum[ch][n][L_subframeTCX - 1];
+                }
 
                 /* power spectrum: MDCT^2 + MDST^2 */
                 powerSpec[ch][n * L_subframeTCX] = sts[ch]->hTcxEnc->spectrum[n][0] * sts[ch]->hTcxEnc->spectrum[n][0];
diff --git a/lib_enc/ivas_mct_enc_mct.c b/lib_enc/ivas_mct_enc_mct.c
old mode 100644
new mode 100755
index 228f48b305453884a1c4a8fef64abc9b2a22190b..50982e2e52f08ace13a7ef232d7bc34f4a3831d4
--- a/lib_enc/ivas_mct_enc_mct.c
+++ b/lib_enc/ivas_mct_enc_mct.c
@@ -700,6 +700,9 @@ void apply_MCT_enc(
                     {
                         v_multc( sts[ch]->hTcxEnc->spectrum[k], qratio, sts[ch]->hTcxEnc->spectrum[k], L_subframeTCX );
                         v_multc( mdst_spectrum[ch][k], qratio, mdst_spectrum[ch][k], L_subframeTCX );
+#ifdef FIX_483b
+                        set_zero( inv_spectrum[ch][k], L_subframeTCX );
+#endif
                     }
                     hMCT->mc_global_ild[ch] = 0;
                 }
diff --git a/lib_enc/ivas_stereo_mdct_core_enc.c b/lib_enc/ivas_stereo_mdct_core_enc.c
old mode 100644
new mode 100755
index 03fcad485a8493450e60aa5f673c257d11a2444c..c8e3dcfcd4423d95102842b379a6f6aa37369edc
--- a/lib_enc/ivas_stereo_mdct_core_enc.c
+++ b/lib_enc/ivas_stereo_mdct_core_enc.c
@@ -223,6 +223,10 @@ void stereo_mdct_core_enc(
         inv_spectrum[ch][1] = quantized_spectrum[ch][1];
         mdst_spectrum[ch][0] = mdst_spectrum_long[ch];
         mdst_spectrum[ch][1] = mdst_spectrum_long[ch] + N_TCX10_MAX;
+#ifdef FIX_483b
+        sts[ch]->hTcxEnc->tns_ms_flag[0] = 0;
+        sts[ch]->hTcxEnc->tns_ms_flag[1] = 0;
+#endif
     }
 
 
@@ -275,7 +279,11 @@ void stereo_mdct_core_enc(
 
         for ( n = 0; n < nSubframes; n++ )
         {
+#ifdef FIX_483b
+            if ( sts[ch]->hTcxEnc->tns_ms_flag[n] )
+#else
             if ( !sts[ch]->hTcxEnc->fUseTns[n] )
+#endif
             {
                 /* power spectrum: MDCT^2 + MDST^2 */
                 for ( i = 0; i < L_subframeTCX; i++ )
@@ -286,14 +294,19 @@ void stereo_mdct_core_enc(
             }
             else
             {
-                /* power spectrum: MDCT^2 + MDST^2 */
-                powerSpecMsInv[ch][n][0] = inv_spectrum[ch][n][0] * inv_spectrum[ch][n][0];
-                for ( i = 1; i < L_subframeTCX - 1; i++ )
+#ifdef FIX_483b
+                if ( hStereoMdct->mdct_stereo_mode[n] != SMDCT_DUAL_MONO )
+#endif
                 {
-                    float mdst = ( inv_spectrum[ch][n][i + 1] - inv_spectrum[ch][n][i - 1] ); /* An MDST estimate */
-                    powerSpecMsInv[ch][n][i] = mdst * mdst + inv_spectrum[ch][n][i] * inv_spectrum[ch][n][i];
+                    /* power spectrum: MDCT^2 + MDST^2 */
+                    powerSpecMsInv[ch][n][0] = inv_spectrum[ch][n][0] * inv_spectrum[ch][n][0];
+                    for ( i = 1; i < L_subframeTCX - 1; i++ )
+                    {
+                        float mdst = ( inv_spectrum[ch][n][i + 1] - inv_spectrum[ch][n][i - 1] ); /* An MDST estimate */
+                        powerSpecMsInv[ch][n][i] = mdst * mdst + inv_spectrum[ch][n][i] * inv_spectrum[ch][n][i];
+                    }
+                    powerSpecMsInv[ch][n][L_subframeTCX - 1] = inv_spectrum[ch][n][L_subframeTCX - 1] * inv_spectrum[ch][n][L_subframeTCX - 1];
                 }
-                powerSpecMsInv[ch][n][L_subframeTCX - 1] = inv_spectrum[ch][n][L_subframeTCX - 1] * inv_spectrum[ch][n][L_subframeTCX - 1];
 
                 /* power spectrum: MDCT^2 + MDST^2 */
                 powerSpec[ch][n * L_subframeTCX] = sts[ch]->hTcxEnc->spectrum[n][0] * sts[ch]->hTcxEnc->spectrum[n][0];
diff --git a/lib_enc/ivas_stereo_mdct_stereo_enc.c b/lib_enc/ivas_stereo_mdct_stereo_enc.c
index 138c9436d6664a3c16dce55a5761fcd866156e0e..97c9ebe7ff3121542df08033e79802da2d3afb81 100755
--- a/lib_enc/ivas_stereo_mdct_stereo_enc.c
+++ b/lib_enc/ivas_stereo_mdct_stereo_enc.c
@@ -563,7 +563,12 @@ void ms_inv_mask_processing(
 {
     int16_t sfb;
     STEREO_MDCT_BAND_PARAMETERS *sfbConf;
+#ifdef FIX_483b
+    int16_t nSubframes, L_subframeTCX;
 
+    nSubframes = ( sts[0]->hTcxEnc->tcxMode == TCX_20 ) ? 1 : NB_DIV;
+    L_subframeTCX = sts[0]->hTcxEnc->L_frameTCX / nSubframes;
+#endif
     sfbConf = ( sts[0]->core == TCX_20_CORE ) ? &hStereoMdct->stbParamsTCX20 : &hStereoMdct->stbParamsTCX10;
 
     if ( sts[0]->last_core == ACELP_CORE )
@@ -588,6 +593,15 @@ void ms_inv_mask_processing(
         }
     }
 
+#ifdef FIX_483b
+    /* set rest of inverse spectrum to zero */
+    if ( L_subframeTCX > sfbConf->sfbOffset[maxSfb] )
+    {
+        set_zero( &x_inv_0[sfbConf->sfbOffset[maxSfb]], L_subframeTCX - sfbConf->sfbOffset[maxSfb] );
+        set_zero( &x_inv_1[sfbConf->sfbOffset[maxSfb]], L_subframeTCX - sfbConf->sfbOffset[maxSfb] );
+    }
+#endif
+
     return;
 }