diff --git a/src/system/FileDescriptor.cxx b/src/system/FileDescriptor.cxx
index 7717a7a62..a6e176166 100644
--- a/src/system/FileDescriptor.cxx
+++ b/src/system/FileDescriptor.cxx
@@ -30,6 +30,7 @@
 #include "config.h"
 #include "FileDescriptor.hxx"
 
+#include <assert.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 
diff --git a/src/system/FileDescriptor.hxx b/src/system/FileDescriptor.hxx
index c7203eb63..61b8a0aa4 100644
--- a/src/system/FileDescriptor.hxx
+++ b/src/system/FileDescriptor.hxx
@@ -35,7 +35,6 @@
 
 #include <utility>
 
-#include <assert.h>
 #include <unistd.h>
 #include <sys/types.h>