diff --git a/src/config.c b/src/config.c
index 36c2e42b7..e506060a9 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1685,7 +1685,7 @@ int rewriteConfigOverwriteFile(char *configfile, sds content) {
         return retval;
     }
 
-#ifdef _GNU_SOURCE
+#if defined(_GNU_SOURCE) && !defined(__HAIKU__)
     fd = mkostemp(tmp_conffile, O_CLOEXEC);
 #else
     /* There's a theoretical chance here to leak the FD if a module thread forks & execv in the middle */
diff --git a/src/zmalloc.h b/src/zmalloc.h
index 1ff66a635..491013a85 100644
--- a/src/zmalloc.h
+++ b/src/zmalloc.h
@@ -74,12 +74,16 @@
 
 #if !defined(NO_MALLOC_USABLE_SIZE) && \
     (defined(__GLIBC__) || defined(__FreeBSD__) || \
+     defined(__DragonFly__) || defined(__HAIKU__) || \
      defined(USE_MALLOC_USABLE_SIZE))
 
 /* Includes for malloc_usable_size() */
 #ifdef __FreeBSD__
 #include <malloc_np.h>
 #else
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
 #include <malloc.h>
 #endif