diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 44ada37167..b24efc772b 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-17  Kamil Rytarowski  <n54@gmx.com>
+
+	* gdb.base/attach-twice.c: Include "sys/types.h".
+	(PTRACE_ATTACH): Add fallback definition.
+	(main): Pass `0' to the 4th argument of `ptrace'.
+
 2020-04-17  Kamil Rytarowski  <n54@gmx.com>
 
 	* gdb.base/fork-running-state.c: Include "signal.h".
diff --git a/gdb/testsuite/gdb.base/attach-twice.c b/gdb/testsuite/gdb.base/attach-twice.c
index 9299b3abf8..31cd087453 100644
--- a/gdb/testsuite/gdb.base/attach-twice.c
+++ b/gdb/testsuite/gdb.base/attach-twice.c
@@ -18,9 +18,14 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <sys/types.h>
 #include <sys/ptrace.h>
 #include <errno.h>
 
+#ifndef PTRACE_ATTACH
+#define PTRACE_ATTACH PT_ATTACH
+#endif
+
 int
 main (void)
 {
@@ -33,7 +38,9 @@ main (void)
       exit (1);
     case 0:
       errno = 0;
-      ptrace (PTRACE_ATTACH, getppid (), NULL, NULL);
+      /* The 4th argument to ptrace () is 0 on purpose, as it is compatible
+	 between kernels that accept void* (like Linux) and int (NetBSD).  */
+      ptrace (PTRACE_ATTACH, getppid (), NULL, 0);
       if (errno != 0)
 	perror ("PTRACE_ATTACH");
       break;