diff --git a/lib_com/options.h b/lib_com/options.h
index 8b6b40f990c1cfc91d230b1e5b02713c95edf160..7fa610801bd2a2942126d5f7c449a42ed0a3fe3e 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -102,6 +102,7 @@
 #define FIX_2459_USAN_AMR_SIDSTART                      /* FhG: basop issue 2459: fix msan complaint */
 #define FIX_2458_USAN_NULLPTR_WITH_ZERO_OFFSET          /* FhG: basop issue 2458: avoid indexing into null pointer */
 #define HARM_2456_APPLY_SCALE                           /* FhG basop issue 2456: Harmonize apply_scale_ind(), apply_scale_ivas_fx() */
+#define HARM_2454_TCX_RES_Q_SPEC                        /* FhG: harmonization of tcx_res_Q_spec_fx() and tcx_res_Q_spec_ivas_fx() */
 
 /* #################### End BE switches ################################## */
 
diff --git a/lib_enc/cod_tcx_fx.c b/lib_enc/cod_tcx_fx.c
index 111805d4292c6e2ef023049232a710d75c6cadf2..71d22d2a8c85a1b1bfa90e000c0c5ef421651146 100644
--- a/lib_enc/cod_tcx_fx.c
+++ b/lib_enc/cod_tcx_fx.c
@@ -3585,11 +3585,19 @@ void QuantizeTCXSpectrum_fx(
             resQBits = tcx_res_Q_gain_fx( gain_tcx_opt_fx, gain_tcx_opt_e, gain_tcx_fx, gain_tcx_e, sqQ + L_spec, resQTargetBits );
             IF( st->tcxonly )
             {
+#ifdef HARM_2454_TCX_RES_Q_SPEC
+                resQBits = tcx_res_Q_spec_fx( x_orig_fx, x_orig_e, spectrum_fx, *spectrum_e, L_spec, *gain_tcx_fx, *gain_tcx_e, sqQ + L_spec, resQTargetBits, resQBits, st->hTcxCfg->sq_rounding, NULL );
+#else
                 resQBits = tcx_res_Q_spec_ivas_fx( x_orig_fx, x_orig_e, spectrum_fx, *spectrum_e, L_spec, *gain_tcx_fx, *gain_tcx_e, sqQ + L_spec, resQTargetBits, resQBits, st->hTcxCfg->sq_rounding, NULL );
+#endif
             }
             ELSE
             {
+#ifdef HARM_2454_TCX_RES_Q_SPEC
+                resQBits = tcx_res_Q_spec_fx( x_orig_fx, x_orig_e, spectrum_fx, *spectrum_e, L_spec, *gain_tcx_fx, *gain_tcx_e, sqQ + L_spec, resQTargetBits, resQBits, st->hTcxCfg->sq_rounding, lf_deemph_fact_fx );
+#else
                 resQBits = tcx_res_Q_spec_ivas_fx( x_orig_fx, x_orig_e, spectrum_fx, *spectrum_e, L_spec, *gain_tcx_fx, *gain_tcx_e, sqQ + L_spec, resQTargetBits, resQBits, st->hTcxCfg->sq_rounding, lf_deemph_fact_fx );
+#endif
             }
         }
     }
diff --git a/lib_enc/prot_fx_enc.h b/lib_enc/prot_fx_enc.h
index 39748c73c49f8dd0e039da3ec0cc4ffe00112ad4..fc3c7928c2cbb4bf573d19419ebef5ae495af60a 100644
--- a/lib_enc/prot_fx_enc.h
+++ b/lib_enc/prot_fx_enc.h
@@ -1351,6 +1351,7 @@ Word16 tcx_res_Q_spec_fx(
     Word16 sq_round,
     const Word16 lf_deemph_factors[] );
 
+#ifndef HARM_2454_TCX_RES_Q_SPEC
 Word16 tcx_res_Q_spec_ivas_fx(
     Word32 *x_orig,
     Word16 x_orig_e,
@@ -1364,7 +1365,7 @@ Word16 tcx_res_Q_spec_ivas_fx(
     Word16 bits,
     Word16 sq_round,
     const Word16 lf_deemph_factors[] );
-
+#endif
 /* compute noise-measure flags for spectrum filling and quantization (0: tonal, 1: noise-like) */
 void ComputeSpectrumNoiseMeasure_fx(
     const Word32 *powerSpec,
diff --git a/lib_enc/tcx_utils_enc_fx.c b/lib_enc/tcx_utils_enc_fx.c
index 01fe7c1d58ac2f582c47b089761708bf8ade47fc..1ada17a8f538da95f1d1486180467732134ddce6 100644
--- a/lib_enc/tcx_utils_enc_fx.c
+++ b/lib_enc/tcx_utils_enc_fx.c
@@ -3388,6 +3388,7 @@ Word16 tcx_res_Q_gain_fx(
     return bits;
 }
 
+#ifndef HARM_2454_TCX_RES_Q_SPEC
 Word16 tcx_res_Q_spec_fx(
     Word32 *x_orig,
     Word16 x_orig_e,
@@ -3568,6 +3569,9 @@ Word16 tcx_res_Q_spec_fx(
 
 
 Word16 tcx_res_Q_spec_ivas_fx(
+#else
+Word16 tcx_res_Q_spec_fx(
+#endif
     Word32 *x_orig,
     Word16 x_orig_e,
     Word32 *x_Q,