diff --git a/lib_com/options.h b/lib_com/options.h
index 5390fd919b424d1cbb634d663986f69f38f87b69..87301cd49cc005dbbcfbcaf571407256cf467c5a 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -132,6 +132,7 @@
 #define FIX_FLOAT_1578_OMASA_REND_SPIKES                /* Nokia: Float issue 1578: Fix spikes and collapsed perception in OMASA/MASA rendering to FOA/HOA */
 #define FIX_1521_SBA_LOUDNESS_STEREO                    /* FhG: issue 1521: Fix loudness for SBA to stereo rendering */
 #define FIX_1559                                        /* Eri/FhG: fix for Issue 1559 in FD CNG with bitrate/bw switching */
+#define FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT          /* Dolby: fix 2580: use dynamic length denominator for average energy in unclr_calc_corr_features_fx() */
 
 /* ##################### End NON-BE switches ########################### */
 
diff --git a/lib_enc/ivas_stereo_ica_enc_fx.c b/lib_enc/ivas_stereo_ica_enc_fx.c
index 234652072aafb5da36bdc5e843e522bd6928ad00..0b9a2c9f9c0e21eae770e321365b1b3c1342b107 100644
--- a/lib_enc/ivas_stereo_ica_enc_fx.c
+++ b/lib_enc/ivas_stereo_ica_enc_fx.c
@@ -2220,7 +2220,13 @@ static void unclr_calc_corr_features_fx(
     Word16 *corrEst_ncorr_exp )
 {
     Word16 i, corrLagMax, d_corrLagMax, tempLen, k;
+#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT
+    Word16 inv_len_exp;
+#endif
     Word32 num, den;
+#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT
+    Word32 inv_len;
+#endif
     Word32 corrL, corrR, ener, ener_side, mono_i, side_i, ic_Lm, ic_Rm, tdm_es_em, m_corrL_corrR, d_corrL_corrR;
     Word32 sum_prod, corrEstMax;
     Word16 corrL_exp, corrR_exp, ener_exp, ener_side_exp, sum_prod_exp, exp, exp1, exp2, num_exp, den_exp;
@@ -2268,6 +2274,18 @@ static void unclr_calc_corr_features_fx(
     }
 
     /* average energy of L and R channels */
+#ifdef FIX_NONBE_2580_USE_LENGTH_NOT_CONSTANT
+    inv_len = BASOP_Util_Divide3232_Scale_newton( ONE_IN_Q31, L_deposit_l( length ), &inv_len_exp ); /* Q31-inv_len_exp */
+
+    hStereoClassif->ave_ener_L_fx = Mpy_32_32( hStereoTCA->E1_mem_fx, inv_len ); /* Q31-hStereoClassif->ave_ener_L_fx_e */
+    move32();
+    hStereoClassif->ave_ener_L_fx_e = add( hStereoTCA->E1_mem_exp, inv_len_exp );
+    move16();
+    hStereoClassif->ave_ener_R_fx = Mpy_32_32( hStereoTCA->E2_mem_fx, inv_len ); /* Q31-hStereoClassif->ave_ener_R_fx_e */
+    move32();
+    hStereoClassif->ave_ener_R_fx_e = add( hStereoTCA->E2_mem_exp, inv_len_exp );
+    move16();
+#else
     hStereoClassif->ave_ener_L_fx = Mpy_32_32( hStereoTCA->E1_mem_fx, 13421772 /* 1/length in Q31*/ ); /* Q31-hStereoClassif->ave_ener_L_fx_e */
     move32();
     hStereoClassif->ave_ener_L_fx_e = hStereoTCA->E1_mem_exp;
@@ -2276,6 +2294,7 @@ static void unclr_calc_corr_features_fx(
     move32();
     hStereoClassif->ave_ener_R_fx_e = hStereoTCA->E2_mem_exp;
     move16();
+#endif
 
     /* unnormalized L/R correlation */
     IF( sum_prod )