diff --git a/src/MISC/fix_imd.cpp b/src/MISC/fix_imd.cpp
index 87c6886864..abba37cf3f 100644
--- a/src/MISC/fix_imd.cpp
+++ b/src/MISC/fix_imd.cpp
@@ -413,8 +413,8 @@ typedef struct {
   int sd;                  /* socket file descriptor */
 } imdsocket;
 
-static int   imdsock_init(void);
-static void *imdsock_create(void);
+static int   imdsock_init();
+static void *imdsock_create();
 static int   imdsock_bind(void *, int);
 static int   imdsock_listen(void *);
 static void *imdsock_accept(void *);  /* return new socket */
@@ -1160,7 +1160,7 @@ void FixIMD::post_force_respa(int vflag, int ilevel, int /*iloop*/)
 
 /* ---------------------------------------------------------------------- */
 /* local memory usage. approximately. */
-double FixIMD::memory_usage(void)
+double FixIMD::memory_usage()
 {
   return static_cast<double>(num_coords+maxbuf+imd_forces)*size_one;
 }
@@ -1178,7 +1178,7 @@ double FixIMD::memory_usage(void)
  *   Socket interface, abstracts machine dependent APIs/routines.
  ***************************************************************************/
 
-int imdsock_init(void) {
+int imdsock_init() {
 #if defined(_MSC_VER) || defined(__MINGW32__)
   int rc = 0;
   static int initialized=0;
@@ -1197,7 +1197,7 @@ int imdsock_init(void) {
 }
 
 
-void * imdsock_create(void) {
+void * imdsock_create() {
   imdsocket * s;
 
   s = (imdsocket *) malloc(sizeof(imdsocket));
diff --git a/src/MISC/pair_srp.cpp b/src/MISC/pair_srp.cpp
index 0fef989c88..456d45c0ae 100644
--- a/src/MISC/pair_srp.cpp
+++ b/src/MISC/pair_srp.cpp
@@ -359,11 +359,11 @@ void PairSRP::settings(int narg, char **arg)
   }
 
   // settings
-  midpoint = 0;
-  min = 0;
+  midpoint = false;
+  min = false;
 
-  if (strcmp(arg[2],"min") == 0) min = 1;
-  else if (strcmp(arg[2],"mid") == 0) midpoint = 1;
+  if (strcmp(arg[2],"min") == 0) min = true;
+  else if (strcmp(arg[2],"mid") == 0) midpoint = true;
   else
     error->all(FLERR,"Illegal pair_style command");
 
diff --git a/src/ML-IAP/mliap_model_nn.cpp b/src/ML-IAP/mliap_model_nn.cpp
index 2dc29200a1..acbc4a5aba 100644
--- a/src/ML-IAP/mliap_model_nn.cpp
+++ b/src/ML-IAP/mliap_model_nn.cpp
@@ -156,8 +156,8 @@ void MLIAPModelNN::read_coeffs(char *coefffilename)
       memory->create(scale,nelements,2,ndescriptors,"mliap_model:scale");
 
       for (int ilayer = 0; ilayer < nlayers; ilayer++) {
-        tstr = strtok(NULL,"' \t\n\r\f");
-        nnodes[ilayer] = atoi(strtok(NULL,"' \t\n\r\f"));
+        tstr = strtok(nullptr,"' \t\n\r\f");
+        nnodes[ilayer] = atoi(strtok(nullptr,"' \t\n\r\f"));
 
         if (strncmp(tstr, "linear", 6) == 0) activation[ilayer] = 0;
         else if (strncmp(tstr, "sigmoid", 7) == 0) activation[ilayer] = 1;