diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index 893deadd13..c2469b6574 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -3078,7 +3078,7 @@ static int ExpandUserDefined(const char *const pat, expand_T *xp, regmatch_T *re
   *matches = NULL;
   *numMatches = 0;
 
-  char *const retstr = call_user_expand_func((user_expand_func_T)call_func_retstr, xp);
+  char *const retstr = call_user_expand_func(call_func_retstr, xp);
   if (retstr == NULL) {
     return FAIL;
   }
@@ -3150,7 +3150,7 @@ static int ExpandUserList(expand_T *xp, char ***matches, int *numMatches)
 {
   *matches = NULL;
   *numMatches = 0;
-  list_T *const retlist = call_user_expand_func((user_expand_func_T)call_func_retlist, xp);
+  list_T *const retlist = call_user_expand_func(call_func_retlist, xp);
   if (retlist == NULL) {
     return FAIL;
   }
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 014335f5ed..62ad6c057d 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -1226,7 +1226,7 @@ fail:
 ///
 /// @return [allocated] NULL when calling function fails, allocated string
 ///                     otherwise.
-char *call_func_retstr(const char *const func, int argc, typval_T *argv)
+void *call_func_retstr(const char *const func, int argc, typval_T *argv)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_MALLOC
 {
   typval_T rettv;
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index eb1ce5457e..e866ed46a4 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -131,7 +131,7 @@ static const char e_non_numeric_argument_to_z[]
   = N_("E144: Non-numeric argument to :z");
 
 /// ":ascii" and "ga" implementation
-void do_ascii(const exarg_T *const eap)
+void do_ascii(exarg_T *eap)
 {
   char *dig;
   int cc[MAX_MCO];
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 68ea49d53b..25324e36ae 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -1025,10 +1025,9 @@ int delete_first_msg(void)
 }
 
 /// :messages command implementation
-void ex_messages(void *const eap_p)
+void ex_messages(exarg_T *eap)
   FUNC_ATTR_NONNULL_ALL
 {
-  const exarg_T *const eap = (const exarg_T *)eap_p;
   struct msg_hist *p;
 
   if (strcmp(eap->arg, "clear") == 0) {
diff --git a/src/nvim/message.h b/src/nvim/message.h
index 78cd5b7d0e..6fc6674cc2 100644
--- a/src/nvim/message.h
+++ b/src/nvim/message.h
@@ -7,6 +7,7 @@
 
 #include "klib/kvec.h"
 #include "nvim/api/private/defs.h"
+#include "nvim/ex_cmds_defs.h"
 #include "nvim/grid_defs.h"
 #include "nvim/macros.h"
 #include "nvim/types.h"
diff --git a/src/nvim/os/fileio.c b/src/nvim/os/fileio.c
index 846219f720..119a42f074 100644
--- a/src/nvim/os/fileio.c
+++ b/src/nvim/os/fileio.c
@@ -282,9 +282,10 @@ static char writebuf[kRWBufferSize];
 ///
 /// @param[in,out]  rv  RBuffer instance used.
 /// @param[in,out]  fp  File to work with.
-static void file_rb_write_full_cb(RBuffer *const rv, FileDescriptor *const fp)
+static void file_rb_write_full_cb(RBuffer *const rv, void *const fp_in)
   FUNC_ATTR_NONNULL_ALL
 {
+  FileDescriptor *const fp = fp_in;
   assert(fp->wr);
   assert(rv->data == (void *)fp);
   if (rbuffer_size(rv) == 0) {