diff --git a/numpy/core/feature_detection_stdio.h b/numpy/core/feature_detection_stdio.h
index bc14d16d04ff..d8bbfbd8b23c 100644
--- a/numpy/core/feature_detection_stdio.h
+++ b/numpy/core/feature_detection_stdio.h
@@ -1,6 +1,9 @@
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <fcntl.h>
 
+#if 0 /* Only for setup_common.py, not the C compiler */
 off_t ftello(FILE *stream);
 int fseeko(FILE *stream, off_t offset, int whence);
 int fallocate(int, int, off_t, off_t);
+#endif
diff --git a/numpy/core/src/multiarray/convert.c b/numpy/core/src/multiarray/convert.c
index 60c1a1b9b011..8ec0aeefb7af 100644
--- a/numpy/core/src/multiarray/convert.c
+++ b/numpy/core/src/multiarray/convert.c
@@ -23,8 +23,9 @@
 #include "array_coercion.h"
 #include "refcount.h"
 
-int
-fallocate(int fd, int mode, off_t offset, off_t len);
+#if defined(HAVE_FALLOCATE) && defined(__linux__)
+#include <fcntl.h>
+#endif
 
 /*
  * allocate nbytes of diskspace for file fp