diff --git a/lib_com/ari_hm.c b/lib_com/ari_hm.c
index afcdf52ad67c27b23a11034f2d5b7e20a97a2068..3e83529bbb44ad387c3eb534eb322d987a54f92b 100644
--- a/lib_com/ari_hm.c
+++ b/lib_com/ari_hm.c
@@ -273,8 +273,7 @@ void tcx_hm_modify_envelope(
 )
 {
 #ifdef FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI
-    int16_t h, x;
-    int32_t k;
+    int32_t h, x, k;
 #else
     int16_t k, h, x;
 #endif
@@ -295,25 +294,12 @@ void tcx_hm_modify_envelope(
 
     while ( k <= L_frame + kTcxHmParabolaHalfWidth - 1 )
     {
-#ifdef FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI
-        int32_t tmp;
-#endif
-
-#ifdef FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI
-        for ( x = (int16_t) max( 0, k - kTcxHmParabolaHalfWidth ); x <= (int16_t) min( k + kTcxHmParabolaHalfWidth, L_frame - 1 ); ++x )
-#else
         for ( x = max( 0, k - kTcxHmParabolaHalfWidth ); x <= min( k + kTcxHmParabolaHalfWidth, L_frame - 1 ); ++x )
-#endif
         {
             env[x] = Mpy_32_16( env[x], inv_shape[x - k + kTcxHmParabolaHalfWidth] );
         }
         ++h;
-#ifdef FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI
-        tmp = ( h * lag );
-        k = tmp >> fract_res;
-#else
         k = ( h * lag ) >> fract_res;
-#endif
     }
 
     return;
diff --git a/lib_com/options.h b/lib_com/options.h
index 2841eb66b10c53c7b012e09e7ad7d963268f76ad..1e139198591a02de8ec45dce93e71796ba8560ed 100755
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -156,7 +156,7 @@
 #define FIX_963_USAN_ERROR                              /* Eri: Issue 963: USAN error in Stereo CNG, division by zero */
 #define FIX_971_LOG2_IDX_GAIN_0                         /* VA: prevent -Inf due to log2(ratio==0) */
 #define FIX_ACCESS_WITHIN_NULL_STRUCT_MC_BW_SWITCHING   /* FhG: fix usan error in MCT with bw swicthing */
-// #define FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI          /* FhG: fix and undef behaviour bug in the harmonic TCX model arithmetic coder */
+#define FIX_966_VAR_OVERFLOW_IN_HARM_MODEL_ARI          /* FhG: fix and undef behaviour bug in the harmonic TCX model arithmetic coder */
 #define FIX_983_DISC_ISM_DIGEST_NUM_OBJS                /* FhG: issue #983: the discrete ISM digest function uses the wrong number of objects */