diff --git a/src/FEP/fix_adapt_fep.cpp b/src/FEP/fix_adapt_fep.cpp
index c32b44b081..e0c5868e96 100644
--- a/src/FEP/fix_adapt_fep.cpp
+++ b/src/FEP/fix_adapt_fep.cpp
@@ -48,9 +48,9 @@ enum{DIAMETER, CHARGE};
 FixAdaptFEP::FixAdaptFEP(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg)
 {
-  if (narg < 5) error->all(FLERR,"Illegal fix adapt/fep command");
+  if (narg < 5) utils::missing_cmd_args(FLERR,"fix adapt/fep", error);
   nevery = utils::inumeric(FLERR,arg[3],false,lmp);
-  if (nevery < 0) error->all(FLERR,"Illegal fix adapt/fep command");
+  if (nevery < 0) error->all(FLERR,"Illegal fix adapt/fep every value {}", nevery);
 
   dynamic_group_allow = 1;
   create_attribute = 1;
@@ -62,21 +62,21 @@ FixAdaptFEP::FixAdaptFEP(LAMMPS *lmp, int narg, char **arg) :
   int iarg = 4;
   while (iarg < narg) {
     if (strcmp(arg[iarg],"pair") == 0) {
-      if (iarg+6 > narg) error->all(FLERR,"Illegal fix adapt/fep command");
+      if (iarg+6 > narg) utils::missing_cmd_args(FLERR,"fix adapt/fep pair", error);
       nadapt++;
       iarg += 6;
     } else if (strcmp(arg[iarg],"kspace") == 0) {
-      if (iarg+2 > narg) error->all(FLERR,"Illegal fix adapt/fep command");
+      if (iarg+2 > narg) utils::missing_cmd_args(FLERR,"fix adapt/fep kspace", error);
       nadapt++;
       iarg += 2;
     } else if (strcmp(arg[iarg],"atom") == 0) {
-      if (iarg+4 > narg) error->all(FLERR,"Illegal fix adapt/fep command");
+      if (iarg+4 > narg) utils::missing_cmd_args(FLERR,"fix adapt/fep atom", error);
       nadapt++;
       iarg += 4;
     } else break;
   }
 
-  if (nadapt == 0) error->all(FLERR,"Illegal fix adapt/fep command");
+  if (nadapt == 0) error->all(FLERR,"Nothing to adapt in fix adapt/fep command");
   adapt = new Adapt[nadapt];
 
   // parse keywords
@@ -136,11 +136,11 @@ FixAdaptFEP::FixAdaptFEP(LAMMPS *lmp, int narg, char **arg) :
 
   while (iarg < narg) {
     if (strcmp(arg[iarg],"reset") == 0) {
-      if (iarg+2 > narg) error->all(FLERR,"Illegal fix adapt/fep command");
+      if (iarg+2 > narg) utils::missing_cmd_args(FLERR,"fix adapt/fep reset", error);
       resetflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"scale") == 0) {
-      if (iarg+2 > narg) error->all(FLERR,"Illegal fix adapt/fep command");
+      if (iarg+2 > narg) utils::missing_cmd_args(FLERR,"fix adapt/fep scale", error);
       scaleflag = utils::logical(FLERR,arg[iarg+1],false,lmp);
       iarg += 2;
     } else if (strcmp(arg[iarg],"after") == 0) {
@@ -208,7 +208,7 @@ void FixAdaptFEP::post_constructor()
   id_fix_diam = nullptr;
   id_fix_chg = nullptr;
 
-  if (diam_flag) {
+  if (diam_flag && atom->radius_flag) {
     id_fix_diam = utils::strdup(id + std::string("_FIX_STORE_DIAM"));
     fix_diam = dynamic_cast<FixStoreAtom *>(
       modify->add_fix(fmt::format("{} {} STORE/ATOM 1 0 0 1", id_fix_diam,group->names[igroup])));
@@ -226,7 +226,7 @@ void FixAdaptFEP::post_constructor()
     }
   }
 
-  if (chgflag) {
+  if (chgflag && atom->q_flag) {
     id_fix_chg = utils::strdup(id + std::string("_FIX_STORE_CHG"));
     fix_chg = dynamic_cast<FixStoreAtom *>(
       modify->add_fix(fmt::format("{} {} STORE/ATOM 1 0 0 1",id_fix_chg,group->names[igroup])));
@@ -267,9 +267,9 @@ void FixAdaptFEP::init()
 
     ad->ivar = input->variable->find(ad->var);
     if (ad->ivar < 0)
-      error->all(FLERR,"Variable name for fix adapt/fep does not exist");
+      error->all(FLERR,"Variable name {} for fix adapt/fep does not exist", ad->var);
     if (!input->variable->equalstyle(ad->ivar))
-      error->all(FLERR,"Variable for fix adapt/fep is invalid style");
+      error->all(FLERR,"Variable {} for fix adapt/fep is invalid style", ad->var);
 
     if (ad->which == PAIR) {
       anypair = 1;
@@ -285,8 +285,9 @@ void FixAdaptFEP::init()
       if (ptr == nullptr)
         error->all(FLERR,"Fix adapt/fep pair style param not supported");
 
-      ad->pdim = 2;
-      if (ad->pdim == 0) ad->scalar = (double *) ptr;
+      if (ad->pdim != 2)
+        error->all(FLERR,"Pair style parameter {} is not compatible with fix adapt/fep", ad->pparam);
+
       if (ad->pdim == 2) ad->array = (double **) ptr;
 
       // if pair hybrid, test that ilo,ihi,jlo,jhi are valid for sub-style