diff --git a/lib_com/options.h b/lib_com/options.h
index 6857712c5dcc017caf34bbca7bb271d112e80720..92f36b8b8bd6c20832382bf52568de06af44c09b 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -87,6 +87,7 @@
 #define TMP_1342_WORKAROUND_DEC_FLUSH_BROKEN_IN_SR      /* FhG: Temporary workaround for incorrect implementation of decoder flush with split rendering */
 #define NONBE_1122_KEEP_EVS_MODE_UNCHANGED              /* FhG: Disables fix for issue 1122 in EVS mode to keep BE tests green. This switch should be removed once the 1122 fix is added to EVS via a CR.  */
 #define HARMONIZE_2502_GENERATE_COMFORT_NOISE_DEC       /* FhG: harmonize generate_comfort_noise_dec_fx() and generate_comfort_noise_dec_ivas_fx() */
+#define ISSUE_2653_BUG_EXP                              /* FhG: basop issue 2653: Possible bug regarding exponent handling in function mix_output_block_fx*/
 #define FIX_BASOP_2650_DEC_PRM_TCX                      /* FhG: Simplify calculation of st->bits_frame_core in dec_prm_tcx(), align function name to float */
 #define FIX_2648_IVAS_ISM_DEC_DIGEST_TC                 /* FhG: improvements on ivas_ism_dec_digest_tc_fx() */
 #define BE_FIX_BASOP_2543_MISMATCH_REND_OPEN_FX_FL      /* FhG: Aligns implementation of split rendering init loops in IVAS_REND_Open between float and BASOP */
diff --git a/lib_rend/ivas_reverb_fx.c b/lib_rend/ivas_reverb_fx.c
index 50bd990adfb51eae43a55bc8965c37cc8d6d9de0..e986973023308c3a48ca9ef0f574c2c790fb5706 100644
--- a/lib_rend/ivas_reverb_fx.c
+++ b/lib_rend/ivas_reverb_fx.c
@@ -2232,6 +2232,9 @@ ivas_error ivas_reverb_process_fx(
     IF( mix_signals )
     {
         mix_output_block_fx( hReverb, tmp1_fx, tmp2_fx, &pcm_out_fx[0][i_ts * hReverb->full_block_size], &pcm_out_fx[1][i_ts * hReverb->full_block_size] );
+#ifdef ISSUE_2653_BUG_EXP
+        assert( 0 ); // Finding testcases where this function is called.
+#endif // ISSUE_2653_BUG_EXP
     }
     ELSE
     {