diff --git a/src/runtime/c/pgf/pgf.cxx b/src/runtime/c/pgf/pgf.cxx
index 8766a3fcb..de7d30a2b 100644
--- a/src/runtime/c/pgf/pgf.cxx
+++ b/src/runtime/c/pgf/pgf.cxx
@@ -152,7 +152,7 @@ PgfDB *pgf_boot_ngf_cookie(void *cookie,
 #if defined(__linux__)
                            ssize_t (*readfn)(void *, char *, size_t),
 #else
-                           int (*readfn)(void *, const char *, int),
+                           int (*readfn)(void *, char *, int),
 #endif
                            const char* ngf_path,
                            PgfRevision *revision,
diff --git a/src/runtime/c/pgf/pgf.h b/src/runtime/c/pgf/pgf.h
index 01e6fe843..675ababcc 100644
--- a/src/runtime/c/pgf/pgf.h
+++ b/src/runtime/c/pgf/pgf.h
@@ -267,7 +267,7 @@ PgfDB *pgf_boot_ngf_cookie(void *cookie,
 #if defined(__linux__)
                            ssize_t (*readfn)(void *, char *, size_t),
 #else
-                           int (*readfn)(void *, const char *, int),
+                           int (*readfn)(void *, char *, int),
 #endif
                            const char* ngf_path,
                            PgfRevision *revision,