diff --git a/gdb/disasm-flags.h b/gdb/disasm-flags.h
index 5a7371b0a39..9420e7c478c 100644
--- a/gdb/disasm-flags.h
+++ b/gdb/disasm-flags.h
@@ -24,7 +24,7 @@
 
 /* Flags used to control how GDB's disassembler behaves.  */
 
-enum gdb_disassembly_flag
+enum gdb_disassembly_flag : unsigned
   {
     DISASSEMBLY_SOURCE_DEPRECATED = (0x1 << 0),
     DISASSEMBLY_RAW_INSN = (0x1 << 1),