diff --git a/src/KOKKOS/pair_reaxff_kokkos.cpp b/src/KOKKOS/pair_reaxff_kokkos.cpp
index 2e7f720b61..ef004cf29e 100644
--- a/src/KOKKOS/pair_reaxff_kokkos.cpp
+++ b/src/KOKKOS/pair_reaxff_kokkos.cpp
@@ -1273,9 +1273,9 @@ void PairReaxFFKokkos<DeviceType>::operator()(PairReaxFFComputeLJCoulomb<NEIGHFL
   fxtmp = fytmp = fztmp = 0.0;
 #ifdef HIP_OPT_PAIRREAXLJCOULOMB_BLOCKING
 
-  unsigned short int BLK_SZ=80;
+  const unsigned short int BLK_SZ=64;
   unsigned short int nnz;
-  unsigned short int selected_jj[80];
+  unsigned short int selected_jj[BLK_SZ];
   int jj_current = 0;
 
   while (jj_current < jnum) {
@@ -2068,9 +2068,9 @@ void PairReaxFFKokkos<DeviceType>::operator()(PairReaxBuildListsHalf<NEIGHFLAG>,
 
   #ifdef HIP_OPT_PAIRREAXBUILDLISTSHALF_BLOCKING
 
-  unsigned short int BLK_SZ=80;
+  const unsigned short int BLK_SZ=64;
   unsigned short int nnz;
-  unsigned short int selected_jj[80];
+  unsigned short int selected_jj[BLK_SZ];
   unsigned short int jj_current = 0;
 
 
@@ -3698,9 +3698,9 @@ void PairReaxFFKokkos<DeviceType>::operator()(PairReaxFFComputeTorsion_with_BLOC
   F_FLOAT CdDelta_i = 0.0;
 
 
-  unsigned char BLK_SZ=1;
-  unsigned char nnz_jj;
-  unsigned char selected_jj[1];
+  const unsigned short int BLK_SZ=8;
+  unsigned short int nnz_jj;
+  unsigned short int selected_jj[BLK_SZ];
   #ifdef HIP_OPT_TORSION_PREVIEW
   unsigned int jj_current = jj_start;
   #else
@@ -3788,9 +3788,8 @@ void PairReaxFFKokkos<DeviceType>::operator()(PairReaxFFComputeTorsion_with_BLOC
       for(int k = 0; k < 3; k++) fjtmp[k] = 0.0;
       F_FLOAT CdDelta_j = 0.0;
 
-      unsigned char nnz_kk;
-
-      unsigned char selected_kk[1];
+      unsigned short int nnz_kk;
+      unsigned short int selected_kk[BLK_SZ];
       #ifdef HIP_OPT_TORSION_PREVIEW
       unsigned int kk_current = kk_start;
       #else