diff --git a/include/curl/curl.h b/include/curl/curl.h
index 1df508410..20dd250e8 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -373,6 +373,7 @@ typedef curlioerr (*curl_ioctl_callback)(CURL *handle,
                                          int cmd,
                                          void *clientp);
 
+#ifndef CURL_DID_MEMORY_FUNC_TYPEDEFS
 /*
  * The following typedef's are signatures of malloc, free, realloc, strdup and
  * calloc respectively.  Function pointers of these types can be passed to the
@@ -386,6 +387,7 @@ typedef char *(*curl_strdup_callback)(const char *str);
 typedef void *(*curl_calloc_callback)(size_t nmemb, size_t size);
 
 #define CURL_DID_MEMORY_FUNC_TYPEDEFS
+#endif
 
 /* the kind of data that is passed to information_callback*/
 typedef enum {
diff --git a/lib/curl_memory.h b/lib/curl_memory.h
index cbe3b272b..6f792fffd 100644
--- a/lib/curl_memory.h
+++ b/lib/curl_memory.h
@@ -95,6 +95,7 @@ typedef void (*curl_free_callback)(void *ptr);
 typedef void *(*curl_realloc_callback)(void *ptr, size_t size);
 typedef char *(*curl_strdup_callback)(const char *str);
 typedef void *(*curl_calloc_callback)(size_t nmemb, size_t size);
+#define CURL_DID_MEMORY_FUNC_TYPEDEFS
 #endif
 
 extern curl_malloc_callback Curl_cmalloc;