diff --git a/lib_com/ivas_cnst.h b/lib_com/ivas_cnst.h
index afda1b66f43c4042e4680636f12ea3bd0752ce5f..8f0b7d5f5137e2e773e4c00ddd85cf1739d823cc 100644
--- a/lib_com/ivas_cnst.h
+++ b/lib_com/ivas_cnst.h
@@ -1442,7 +1442,11 @@ typedef enum
 #define SFX_SPAT_BIN_NUM_SUBSAMPLES             64
 #define ITD_MEM_LEN                             (MAX_ITD + SFX_SPAT_BIN_SINC_M)
 #define L_SUBFRAME5MS_48k                       (L_FRAME48k/4)
+#ifdef FIX_421_TD_INT_TUNE
+#define MAX_ANGULAR_STEP                        (0.01f)
+#else
 #define MAX_ANGULAR_STEP                        (1.0f)
+#endif
 #define MAX_ANGULAR_STEP_INV                    ( 1.0f / MAX_ANGULAR_STEP )
 #define MAX_INTERPOLATION_STEPS                 12
 
diff --git a/lib_com/options.h b/lib_com/options.h
index 5ce08d7ec124f75233f22e285fd31313fc7bb998..00f08dd38fc0cd6cab6d0e4dae9a90fcfbe4fcaa 100644
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -149,6 +149,7 @@
 #define SNS_MSVQ                                        /* FhG: contribution 33 - MSVQ for SNS parameters at stereo mid bitrates */
 
 #define PARAMMC_SHORT_ENC_MDFT                          /* FhG: Issue 410: complexity optimization for parametric Multichannel modes */
+#define FIX_421_TD_INT_TUNE                             /* Eri: Issue 421: Increase use of interpolation in TD renderer filter transition */
 
 /* ################## End DEVELOPMENT switches ######################### */
 /* clang-format on */