diff --git a/Library/Convert.cpp b/Library/Convert.cpp
index 4ac4df3..a994d2d 100644
--- a/Library/Convert.cpp
+++ b/Library/Convert.cpp
@@ -304,7 +304,7 @@ EXTERNC int isempty(char *str)
     return 1;
 }
 
-EXTERNC unsigned int isdelim(char c, char *delim)
+EXTERNC unsigned int isdelim(char c, const char *delim)
 {
     while (*delim != '\0')
     {
diff --git a/include/convert.h b/include/convert.h
index 4072a8d..d9c7236 100644
--- a/include/convert.h
+++ b/include/convert.h
@@ -12,7 +12,7 @@ extern "C"
     int isempty(char *str);
     int isalpha(int c);
     int isupper(int c);
-    unsigned int isdelim(char c, char *delim);
+    unsigned int isdelim(char c, const char *delim);
     long abs(long i);
     void swap(char *x, char *y);
     char *reverse(char *Buffer, int i, int j);