diff --git a/ivlpp/lexor.lex b/ivlpp/lexor.lex
index 960d74045..519a931fd 100644
--- a/ivlpp/lexor.lex
+++ b/ivlpp/lexor.lex
@@ -1,7 +1,7 @@
 %option prefix="yy"
 %{
 /*
- * Copyright (c) 1999-2024 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2025 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -1080,17 +1080,17 @@ static void def_add_arg(void)
 	 to us to chop it up to name and value. */
     if ( (val=strchr(arg,'=')) ) {
 	  *val++ = 0;
-	  while (*val && isspace(*val)) val += 1;
+	  while (*val && isspace((int)*val)) val += 1;
 
 	  val_length = strlen(val);
-	  while (val_length>0 && isspace(val[val_length-1])) {
+	  while (val_length>0 && isspace((int)val[val_length-1])) {
 		val_length -= 1;
 		val[val_length] = 0;
 	  }
 
 	    /* Strip white space from between arg and "=". */
 	  length = strlen(arg);
-	  while (length>0 && isspace(arg[length-1])) {
+	  while (length>0 && isspace((int)arg[length-1])) {
 		length -= 1;
 		arg[length] = 0;
 	  }
diff --git a/vpi/v2009_string.c b/vpi/v2009_string.c
index 4ffcd1108..241e6f2e1 100644
--- a/vpi/v2009_string.c
+++ b/vpi/v2009_string.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2021 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2012-2025 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -151,7 +151,7 @@ static PLI_INT32 atoi_calltf(ICARUS_VPI_CONST PLI_BYTE8*name)
       vpi_get_value(arg, &value);
       const char*bufp = value.value.str;
       while (bufp && *bufp) {
-	    if (isdigit(*bufp)) {
+	    if (isdigit((int)*bufp)) {
 		  res = (res * 10) + (*bufp - '0');
 		  bufp += 1;
 	    } else if (*bufp == '_') {