diff --git a/utils/path.c b/utils/path.c
index 57e0a14a..c3bed466 100644
--- a/utils/path.c
+++ b/utils/path.c
@@ -952,18 +952,18 @@ PaZOpen(file, mode, ext, path, library, pRealName)
 
 FILE *
 PaOpen(file, mode, ext, path, library, pRealName)
-    char *file;			/* Name of the file to be opened. */
-    char *mode;			/* The file mode, as given to fopen. */
-    char *ext;			/* The extension to be added to the file name,
+    const char *file;		/* Name of the file to be opened. */
+    const char *mode;		/* The file mode, as given to fopen. */
+    const char *ext;		/* The extension to be added to the file name,
 				 * or NULL.  Note:  this string must include
 				 * the dot (or whatever separator you use).
 				 */
-    char *path;			/* A search path:  a list of directory names
+    const char *path;			/* A search path:  a list of directory names
 				 * separated by colons or blanks.  To use
 				 * only the working directory, use "." for
 				 * the path.
 				 */
-    char *library;		/* A 2nd path containing library names.  Can be
+    const char *library;	/* A 2nd path containing library names.  Can be
 				 * NULL to indicate no library.
 				 */
     char **pRealName;		/* Pointer to a location that will be filled
diff --git a/utils/utils.h b/utils/utils.h
index 3778a702..68fa63f2 100644
--- a/utils/utils.h
+++ b/utils/utils.h
@@ -48,7 +48,8 @@ extern int LookupStruct(const char *str, const LookupTable *table_start, int siz
 extern int LookupStructFull(const char *str, const char * const *table, int size);
 extern int PaExpand(const char **, char **, int);
 extern char *nextName(const char **ppath, const char *file, char *dest, int size);
-extern FILE *PaOpen(char *, char *, char *, char *, char *, char **);
+extern FILE *PaOpen(const char *file, const char *mode, const char *ext, const char *path, const char *library,
+                    char **pRealName);
 extern FILE *PaLockOpen(const char *file, const char *mode, const char *ext, const char *path, const char *library,
                         char **pRealName, bool *is_locked, int *fdp);
 extern char *StrDup(char **, const char *);