diff --git a/lib/setup.h b/lib/setup.h
index 36e4c7f147bd3d2d0a76a710b14457de72cd34ba..1d78dc6d2d13ec6438363054f29de0da727de48d 100644
--- a/lib/setup.h
+++ b/lib/setup.h
@@ -244,4 +244,8 @@ typedef struct hostent Curl_addrinfo;
 typedef struct in_addr Curl_ipconnect;
 #endif
 
+#ifndef SIZEOF_CURL_OFF_T
+#define SIZEOF_CURL_OFF_T sizeof(curl_off_t)
+#endif
+
 #endif /* __CONFIG_H */
diff --git a/src/setup.h b/src/setup.h
index 7e8428d70fe2e15f1061e70f02ca2354c2453aca..340a46a4b555375b3486370bdb7177d7f0760225 100644
--- a/src/setup.h
+++ b/src/setup.h
@@ -112,4 +112,8 @@ int fileno( FILE *stream);
 #define typedef_bool
 #endif
 
+#ifndef SIZEOF_CURL_OFF_T
+#define SIZEOF_CURL_OFF_T sizeof(curl_off_t)
+#endif
+
 #endif /* __SETUP_H */