diff --git a/src/fix_ave_time.cpp b/src/fix_ave_time.cpp
index 7efb8cc8a6..3ac8e68cad 100644
--- a/src/fix_ave_time.cpp
+++ b/src/fix_ave_time.cpp
@@ -79,7 +79,7 @@ FixAveTime::FixAveTime(LAMMPS *lmp, int narg, char **arg) :
 
   int expand = 0;
   char **earg;
-  int *amap;
+  int *amap = nullptr;
   nvalues = utils::expand_args(FLERR,nvalues,&arg[6],mode,earg,lmp,&amap);
   key2col.clear();
 
@@ -101,7 +101,8 @@ FixAveTime::FixAveTime(LAMMPS *lmp, int narg, char **arg) :
       error->all(FLERR, amap[i]+6,"Invalid fix ave/time argument: {}", arg[i]);
 
     val.argindex = argi.get_index1();
-    val.iarg = amap[i] + 6;
+    if (expand) val.iarg = amap[i] + 6;
+    else val.iarg = i + 6;
     val.varlen = 0;
     val.offcol = 0;
     val.id = argi.get_name();
@@ -278,6 +279,7 @@ FixAveTime::FixAveTime(LAMMPS *lmp, int narg, char **arg) :
   if (expand) {
     for (int i = 0; i < nvalues; i++) delete[] earg[i];
     memory->sfree(earg);
+    memory->sfree(amap);
   }
 
   // allocate memory for averaging
diff --git a/src/utils.cpp b/src/utils.cpp
index 0007b11e9c..52d7e5113a 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -860,10 +860,12 @@ int utils::expand_args(const char *file, int line, int narg, char **arg, int mod
     return narg;
   }
 
-  // determine argument offset
+  // determine argument offset, if possible
   int ioffset = 0;
-  for (int i = 0; i < lmp->input->narg; ++i)
-    if (lmp->input->arg[i] == arg[0]) ioffset = i;
+  if (lmp->input->arg) {
+    for (int i = 0; i < lmp->input->narg; ++i)
+      if (lmp->input->arg[i] == arg[0]) ioffset = i;
+  }
 
   // maxarg should always end up equal to newarg, so caller can free earg
 
@@ -1052,7 +1054,6 @@ int utils::expand_args(const char *file, int line, int narg, char **arg, int mod
       if (expandflag) {
 
         // expand wild card string to nlo/nhi numbers
-
         utils::bounds(file, line, wc, 1, nmax, nlo, nhi, lmp->error, iarg + ioffset);
 
         if (newarg + nhi - nlo + 1 > maxarg) {
@@ -1086,7 +1087,11 @@ int utils::expand_args(const char *file, int line, int narg, char **arg, int mod
     }
   }
 
-  if (argmap && *argmap) *argmap = amap;
+  if (argmap)
+    *argmap = amap;
+  else
+    lmp->memory->sfree(amap);
+
   // fprintf(stderr, "NEWARG %d\n",newarg); for (int i = 0; i < newarg; i++) printf("  arg %d: %s %d\n",i,earg[i], amap ? amap[i] : -1);
   return newarg;
 }
diff --git a/unittest/cplusplus/test_advanced_utils.cpp b/unittest/cplusplus/test_advanced_utils.cpp
index 1da9500b35..468f353080 100644
--- a/unittest/cplusplus/test_advanced_utils.cpp
+++ b/unittest/cplusplus/test_advanced_utils.cpp
@@ -151,6 +151,10 @@ TEST_F(Advanced_utils, expand_args)
     args[7]            = utils::strdup("c_gofr[*2][2]");
     args[8]            = utils::strdup("c_gofr[*][*]");
 
+    // disable use of input->command and input->arg which point to the last run command right now
+    lmp->input->command = nullptr;
+    lmp->input->arg    = nullptr;
+
     auto narg = utils::expand_args(FLERR, oarg, args, 0, earg, lmp);
     EXPECT_EQ(narg, 16);
     EXPECT_STREQ(earg[0], "v_step");