diff --git a/lib_com/options.h b/lib_com/options.h
index 074d039191490122c3490f21950c73cef83ca8a4..5e967e6e6a26f2caa5917dd6ac1e6862db65f9fc 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -97,6 +97,7 @@
 #define FIX_BASOP_2509_EVS_CONCEAL_UNINIT_MEM           /* FhG: BASOP 2509: st->hTcxCfg->psychParamsCurrent is not initialized */
 #define HARMONIZE_2499_CONFIGUREFDCNGDEC                /* FhG: basop issue 2499: harmonoize configureFdCngDec */
 #define FIX_BASOP_2530_IVAS_DECISION_MAT                /* VA: Fix ambiguous usage of extract_l() */
+#define HARMONIZE_2543_SQ_gain                          /* FhG: Harmonize SQ_gain */
 
 
 /* #################### End BE switches ################################## */
diff --git a/lib_enc/cod_tcx_fx.c b/lib_enc/cod_tcx_fx.c
index 72a8d01d37359fb0bb4b8a44c9ba66a676cbc116..b16e25b0dbab46ce8b4148230e3581166d35a76c 100644
--- a/lib_enc/cod_tcx_fx.c
+++ b/lib_enc/cod_tcx_fx.c
@@ -1432,10 +1432,18 @@ void QuantizeSpectrum_fx(
 
                 /* Quantize original spectrum */
 
+#ifdef HARMONIZE_2543_SQ_gain
+                sqGain = SQ_gain_fx( OriginalSpectrum, OriginalSpectrum_e,
+                                     shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ),
+                                     L_spec,
+                                     &sqGain_e,
+                                     EVS_MONO );
+#else
                 sqGain = SQ_gain_fx( OriginalSpectrum, OriginalSpectrum_e,
                                      shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ),
                                      L_spec,
                                      &sqGain_e );
+#endif
 
                 tcx_scalar_quantization_fx( OriginalSpectrum, OriginalSpectrum_e,
                                             sqQ,
@@ -1524,10 +1532,18 @@ void QuantizeSpectrum_fx(
                 PeriodicityIndex = -1;
                 move16();
 
+#ifdef HARMONIZE_2543_SQ_gain
+                sqGain = SQ_gain_fx( spectrum, *spectrum_e,
+                                     shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ),
+                                     L_spec,
+                                     &sqGain_e,
+                                     EVS_MONO );
+#else
                 sqGain = SQ_gain_fx( spectrum, *spectrum_e,
                                      shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ),
                                      L_spec,
                                      &sqGain_e );
+#endif
 
                 /* Quantize spectrum */
 
@@ -3027,7 +3043,11 @@ void QuantizeTCXSpectrum_fx(
             }
 
             /* Quantize original spectrum */
+#ifdef HARMONIZE_2543_SQ_gain
+            sqGain_fx = SQ_gain_fx( spectrum_fx, *spectrum_e, ( mult( hTcxEnc->tcx_target_bits_fac, shl( sqTargetBits, 1 ) ) ), L_spec, &sqGain_e, 1 /*signal non-EVS*/ );
+#else
             sqGain_fx = SQ_gain_ivas_fx( spectrum_fx, *spectrum_e, ( mult( hTcxEnc->tcx_target_bits_fac, shl( sqTargetBits, 1 ) ) ), L_spec, &sqGain_e );
+#endif
 
             tcx_scalar_quantization_ivas_fx( spectrum_fx, *spectrum_e, sqQ, L_spec, sqGain_fx, sqGain_e, st->hTcxCfg->sq_rounding, hTcxEnc->memQuantZeros, st->tcxonly );
 
@@ -3118,7 +3138,11 @@ void QuantizeTCXSpectrum_fx(
             }
             ELSE
             {
+#ifdef HARMONIZE_2543_SQ_gain
+                sqGain_fx = SQ_gain_fx( spectrum_fx, *spectrum_e, shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ), L_spec, &sqGain_e, 1 /*signal non-EVS*/ );
+#else
                 sqGain_fx = SQ_gain_ivas_fx( spectrum_fx, *spectrum_e, shl( mult( hTcxEnc->tcx_target_bits_fac, sqTargetBits ), 1 ), L_spec, &sqGain_e );
+#endif
             }
             /* Quantize spectrum */
             tcx_scalar_quantization_ivas_fx( spectrum_fx, *spectrum_e, sqQ, L_spec, sqGain_fx, sqGain_e, st->hTcxCfg->sq_rounding, hTcxEnc->memQuantZeros, st->tcxonly );
diff --git a/lib_enc/prot_fx_enc.h b/lib_enc/prot_fx_enc.h
index d5987061021a9e1c325279704c598954de0e8c1b..824a986dce347b5f02c3aa812c4c2519919c7959 100644
--- a/lib_enc/prot_fx_enc.h
+++ b/lib_enc/prot_fx_enc.h
@@ -1081,6 +1081,16 @@ void AdaptLowFreqEmph_fx(
     const Word16 lg );
 
 /* o  : SQ gain                   */
+#ifdef HARMONIZE_2543_SQ_gain
+Word16 SQ_gain_fx(
+    Word32 x[],         /* i  :  vector to quantize        */
+    Word16 x_e,         /* i  :  exponent                  */
+    Word16 nbitsSQ,     /* i  :  number of bits targeted   */
+    Word16 lg,          /* i  :  vector size (2048 max)    */
+    Word16 *gain_e,     /* o  :  SQ gain exponent          */
+    Word16 element_mode /* i  :  is EVS or not             */
+);
+#else
 Word16 SQ_gain_fx(
     Word32 x[],     /* i  :  vector to quantize        */
     Word16 x_e,     /* i  :  exponent                  */
@@ -1097,6 +1107,7 @@ Word16 SQ_gain_ivas_fx(
     Word16 lg,      /* i  :  vector size (2048 max)    */
     Word16 *gain_e  /* o  : SQ gain exponent          */
 );
+#endif
 
 /* o  : SQ gain                   */
 Word16 SQ_gain_estimate_fx(
diff --git a/lib_enc/tcx_utils_enc_fx.c b/lib_enc/tcx_utils_enc_fx.c
index db3c828d52bb2d82b9d5c4ec1024da803afa06f3..e833af0579ef85d65616b23e1fddd30f2f17a055 100644
--- a/lib_enc/tcx_utils_enc_fx.c
+++ b/lib_enc/tcx_utils_enc_fx.c
@@ -827,7 +827,7 @@ void PsychAdaptLowFreqEmph_fx(
     return;
 }
 
-
+#ifndef HARMONIZE_2543_SQ_gain
 /* o: SQ gain  */
 Word16 SQ_gain_fx(
     Word32 x[],      /* i  :  vector to quantize        */
@@ -941,15 +941,27 @@ Word16 SQ_gain_fx(
 
     return tmp16;
 }
-
+#endif
 
 /* o: SQ gain  */
+#ifdef HARMONIZE_2543_SQ_gain
+Word16 SQ_gain_fx(
+    Word32 x[],         /* i  : vector to quantize        */
+    Word16 x_e,         /* i  : exponent                  */
+    Word16 nbitsSQ,     /* i  : number of bits targeted   */
+    Word16 lg,          /* i  : vector size (2048 max)    */
+    Word16 *gain_e,     /* o  : SQ gain exponent          */
+    Word16 element_mode /* i  : is EVS or not             */
+)
+#else
 Word16 SQ_gain_ivas_fx(
-    Word32 x[],      /* i  : vector to quantize        */
-    Word16 x_e,      /* i  : exponent                  */
-    Word16 nbitsSQ,  /* i  : number of bits targeted   */
-    Word16 lg,       /* i  : vector size (2048 max)    */
-    Word16 *gain_e ) /* o  : SQ gain exponent          */
+    Word32 x[],     /* i  : vector to quantize        */
+    Word16 x_e,     /* i  : exponent                  */
+    Word16 nbitsSQ, /* i  : number of bits targeted   */
+    Word16 lg,      /* i  : vector size (2048 max)    */
+    Word16 *gain_e  /* o  : SQ gain exponent          */
+)
+#endif
 {
     Word16 i, iter, lg_4, s, tmp16;
     Word32 ener, tmp32;
@@ -1009,7 +1021,12 @@ Word16 SQ_gain_ivas_fx(
         s = shl( sub( x_e, s ), 1 );
 
         /* log */
+#ifdef HARMONIZE_2543_SQ_gain
+        test();
+        IF( EQ_32( ener, 1 ) && GT_16( element_mode, EVS_MONO ) )
+#else
         IF( EQ_32( ener, 1 ) )
+#endif
         {
             en[i] = -131072; /* log10(0.01) in Q16 */
             move32();