diff --git include/ptrace.h include/ptrace.h
index dfc5ecd..efea594 100644
--- include/ptrace.h
+++ include/ptrace.h
@@ -44,8 +44,10 @@ struct ptrace_peeksiginfo_args {
 # define PTRACE_SETREGSET      0x4205
 #endif

+#ifndef PTRACE_GETSIGMASK
 #define PTRACE_GETSIGMASK      0x420a
 #define PTRACE_SETSIGMASK      0x420b
+#endif

 #ifndef PTRACE_SECCOMP_GET_FILTER
 #define PTRACE_SECCOMP_GET_FILTER      0x420c