diff --git a/lib_com/options.h b/lib_com/options.h
index a6a4b4944d2337852a2c88a917df8abe2f86b4ea..ba44aa63b9bec86b95ab89e0408f24eeceb4a588 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -164,6 +164,8 @@
 #define FIX_390_EXT_REND_MASA_META_COPY                 /* Nokia: Issue 390: Fixes MASA metadata copying to renderer. */
 #define FIX_392_LATE_REVERB                             /* DLB : Issue 392: keep late reverb by default off when output config is not BINAURAL_ROOM*/
 
+#define FIX_ISM_DTX_CLICKS                              /* FhG: fix for clicks in ISM DTX for inactive to active TCX transitions */
+
 /* ################## End DEVELOPMENT switches ######################### */
 /* clang-format on */
 #endif
diff --git a/lib_com/prot.h b/lib_com/prot.h
index e89037076e09d444ba077fe2b10759fdfece64ec..51d1cb1e20c4df051f2a4f0df8b1ddd961df1176 100644
--- a/lib_com/prot.h
+++ b/lib_com/prot.h
@@ -5856,10 +5856,13 @@ void core_switching_post_enc(
 );
 
 ivas_error core_switching_post_dec(
-    Decoder_State *st,                   /* i/o: decoder state structure                 */
-    float *synth,                        /* i/o: output synthesis                        */
-    float *output,                       /* i/o: LB synth/upsampled LB synth             */
-    float output_mem[],                  /* i  : OLA memory from last TCX/HQ frame       */
+    Decoder_State *st,  /* i/o: decoder state structure                 */
+    float *synth,       /* i/o: output synthesis                        */
+    float *output,      /* i/o: LB synth/upsampled LB synth             */
+    float output_mem[], /* i  : OLA memory from last TCX/HQ frame       */
+#ifdef FIX_ISM_DTX_CLICKS
+    const IVAS_FORMAT ivas_format, /* i  : IVAS format                             */
+#endif
     const int16_t use_cldfb_for_dft,     /* i  : flag to use of CLDFB for DFT Stereo     */
     const int16_t output_frame,          /* i  : frame length                            */
     const int16_t core_switching_flag,   /* i  : ACELP->HQ switching frame flag          */
diff --git a/lib_dec/core_switching_dec.c b/lib_dec/core_switching_dec.c
index c2a3955afba78484d27ac1a564e75a6a9f4d6113..fc331a2e9feddf5613d7087db069c065ce0e6b09 100644
--- a/lib_dec/core_switching_dec.c
+++ b/lib_dec/core_switching_dec.c
@@ -51,7 +51,7 @@
  *---------------------------------------------------------------------*/
 
 static void core_switch_lb_upsamp( Decoder_State *st, float *output );
-static void smoothTransitionMdctStereoDtx( float synth[], const int16_t output_frame, const int16_t delay_comp );
+static void smoothTransitionDtxToTcx( float synth[], const int16_t output_frame, const int16_t delay_comp );
 
 /*---------------------------------------------------------------------*
  * core_switching_pre_dec()
@@ -552,10 +552,13 @@ ivas_error core_switching_pre_dec(
  *---------------------------------------------------------------------*/
 
 ivas_error core_switching_post_dec(
-    Decoder_State *st,                   /* i/o: decoder state structure             */
-    float *synth,                        /* i/o: output synthesis                    */
-    float *output,                       /* i/o: LB synth/upsampled LB synth         */
-    float output_mem[],                  /* i  : OLA memory from last TCX/HQ frame   */
+    Decoder_State *st,  /* i/o: decoder state structure             */
+    float *synth,       /* i/o: output synthesis                    */
+    float *output,      /* i/o: LB synth/upsampled LB synth         */
+    float output_mem[], /* i  : OLA memory from last TCX/HQ frame   */
+#ifdef FIX_ISM_DTX_CLICKS
+    const IVAS_FORMAT ivas_format, /* i  : IVAS format                         */
+#endif
     const int16_t use_cldfb_for_dft,     /* i  : flag to use of CLDFB for DFT Stereo */
     const int16_t output_frame,          /* i  : frame length                        */
     const int16_t core_switching_flag,   /* i  : ACELP->HQ switching flag            */
@@ -677,10 +680,14 @@ ivas_error core_switching_post_dec(
                     synth[i + delay_comp] = ( synth[i + delay_comp] * i + ( tmpDelta - i ) * st->previoussynth[i + delay_comp] ) / tmpDelta;
                 }
 
+#ifdef FIX_ISM_DTX_CLICKS
+                if ( ( st->element_mode == IVAS_CPE_MDCT || ( ivas_format == ISM_FORMAT && st->core == TCX_20_CORE /* <- means TCX in general, TCX10 is forbidden after ACELP */ ) ) && st->last_core_brate <= SID_2k40 && st->core_brate > SID_2k40 )
+#else
                 if ( st->element_mode == IVAS_CPE_MDCT && st->last_core_brate <= SID_2k40 && st->core_brate > SID_2k40 )
+#endif
                 {
                     /* smooth transitions to avoid pops in car noise items */
-                    smoothTransitionMdctStereoDtx( synth, output_frame, delay_comp );
+                    smoothTransitionDtxToTcx( synth, output_frame, delay_comp );
                 }
 
                 /* Reset memories of CLDFBs */
@@ -1245,16 +1252,16 @@ static void core_switch_lb_upsamp(
 }
 
 /*---------------------------------------------------------------------*
- * smoothTransitionMdctStereoDtx()
+ * smoothTransitionDtxToTcx()
  *
- * apply smoothing to the transition part for MDCT-Stereo DTX
+ * apply smoothing to the transition part for inactive to active transitions in DTX
  *---------------------------------------------------------------------*/
 
 #define TRANSITION_SMOOTHING_LEN_16k 15
 #define TRANSITION_SMOOTHING_LEN_32k 31
 #define TRANSITION_SMOOTHING_LEN_48k 47
 
-static void smoothTransitionMdctStereoDtx(
+static void smoothTransitionDtxToTcx(
     float synth[],              /* i/o: synthesis                       */
     const int16_t output_frame, /* i  : output frame length             */
     const int16_t delay_comp    /* i  : delay compensation in samples   */
diff --git a/lib_dec/evs_dec.c b/lib_dec/evs_dec.c
index 23914302375ae1e39dd2cf8bccdc03c1a485d997..0dbc0feafc07ebb98963d8314b762d5e20de0e76 100644
--- a/lib_dec/evs_dec.c
+++ b/lib_dec/evs_dec.c
@@ -276,7 +276,11 @@ ivas_error evs_dec(
          * Postprocessing for ACELP/MDCT core switching
          *---------------------------------------------------------------------*/
 
+#ifdef FIX_ISM_DTX_CLICKS
+        if ( ( error = core_switching_post_dec( st, synth, NULL, NULL, 0, MONO_FORMAT, output_frame, core_switching_flag, 0, -1, EVS_MONO ) ) != IVAS_ERR_OK )
+#else
         if ( ( error = core_switching_post_dec( st, synth, NULL, NULL, 0, output_frame, core_switching_flag, 0, -1, EVS_MONO ) ) != IVAS_ERR_OK )
+#endif
         {
             return error;
         }
diff --git a/lib_dec/ivas_core_dec.c b/lib_dec/ivas_core_dec.c
old mode 100755
new mode 100644
index 0811f9957afe9bb87019a364829083b89bc8d2b7..05c1f41727e87111757dd6ca304ae100226350cc
--- a/lib_dec/ivas_core_dec.c
+++ b/lib_dec/ivas_core_dec.c
@@ -451,7 +451,11 @@ ivas_error ivas_core_dec(
             mvr2r( synth[n], hSCE->save_synth, output_frame );
         }
 
+#ifdef FIX_ISM_DTX_CLICKS
+        if ( ( error = core_switching_post_dec( st, synth[n], output[n], p_output_mem, ( st_ivas != NULL ) ? st_ivas->ivas_format : UNDEFINED_FORMAT, use_cldfb_for_dft, output_frame, 0 /*core_switching_flag*/, sba_dirac_stereo_flag, nchan_out, ( hCPE != NULL ) ? hCPE->last_element_mode : IVAS_SCE ) ) != IVAS_ERR_OK )
+#else
         if ( ( error = core_switching_post_dec( st, synth[n], output[n], p_output_mem, use_cldfb_for_dft, output_frame, 0 /*core_switching_flag*/, sba_dirac_stereo_flag, nchan_out, ( hCPE != NULL ) ? hCPE->last_element_mode : IVAS_SCE ) ) != IVAS_ERR_OK )
+#endif
         {
             return error;
         }
diff --git a/lib_dec/ivas_mct_dec.c b/lib_dec/ivas_mct_dec.c
index f39951e0878b8b44fdef53a6cddc0ba6afe4d0f0..eeecd4d8fa38a1b1b501ff5c3e01ee58ae2a0144 100755
--- a/lib_dec/ivas_mct_dec.c
+++ b/lib_dec/ivas_mct_dec.c
@@ -243,7 +243,11 @@ ivas_error ivas_mct_dec(
             }
 
             /* Postprocessing for ACELP/MDCT core switching and synchronization */
+#ifdef FIX_ISM_DTX_CLICKS
+            if ( ( error = core_switching_post_dec( sts[n], synth[n], output[cpe_id * CPE_CHANNELS + n], hCPE->output_mem[1], st_ivas->ivas_format, 0, output_frame, 0 /*core_switching_flag*/, st_ivas->sba_dirac_stereo_flag, -1, hCPE->last_element_mode ) ) != IVAS_ERR_OK )
+#else
             if ( ( error = core_switching_post_dec( sts[n], synth[n], output[cpe_id * CPE_CHANNELS + n], hCPE->output_mem[1], 0, output_frame, 0 /*core_switching_flag*/, st_ivas->sba_dirac_stereo_flag, -1, hCPE->last_element_mode ) ) != IVAS_ERR_OK )
+#endif
             {
                 return error;
             }