diff --git a/qemu-common.h b/qemu-common.h
index ac9985cc6d..093d1198ec 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -1,5 +1,14 @@
 
-/* Common header file that is included by all of qemu.  */
+/* Common header file that is included by all of QEMU.
+ *
+ * This file is supposed to be included only by .c files. No header file should
+ * depend on qemu-common.h, as this would easily lead to circular header
+ * dependencies.
+ *
+ * If a header file uses a definition from qemu-common.h, that definition
+ * must be moved to a separate header file, and the header that uses it
+ * must include that header.
+ */
 #ifndef QEMU_COMMON_H
 #define QEMU_COMMON_H