diff --git a/lib/strtoofft.c b/lib/strtoofft.c
index 7b1a55e30..322a753e3 100644
--- a/lib/strtoofft.c
+++ b/lib/strtoofft.c
@@ -35,15 +35,15 @@ static int get_char(char c, int base);
  * Emulated version of the strtoll function.  This extracts a long long
  * value from the given input string and returns it.
  */
-long long
+curl_off_t
 Curl_strtoll(const char *nptr, char **endptr, int base)
 {
   char *end;
   int is_negative = 0;
   int overflow;
   int i;
-  long long value = 0;
-  long long newval;
+  curl_off_t value = 0;
+  curl_off_t newval;
 
   /* Skip leading whitespace. */
   end = (char *)nptr;
diff --git a/lib/strtoofft.h b/lib/strtoofft.h
index 4b6e6b136..cd512b001 100644
--- a/lib/strtoofft.h
+++ b/lib/strtoofft.h
@@ -37,7 +37,7 @@
 #if HAVE_STRTOLL
 #define strtoofft strtoll
 #else
-long long Curl_strtoll(const char *nptr, char **endptr, int base);
+curl_off_t Curl_strtoll(const char *nptr, char **endptr, int base);
 #define strtoofft Curl_strtoll
 #define NEED_CURL_STRTOLL
 #endif