diff --git a/meson.build b/meson.build
index 6fcf1da5..2c979ccb 100644
--- a/meson.build
+++ b/meson.build
@@ -230,6 +230,16 @@ conf.set(
     ),
     description: 'Is network address and service translation available'
 )
+conf.set(
+    'HAVE_GLIBC_IOCTL',
+    cc.compiles(
+        '''#include <sys/ioctl.h>
+        int ioctl(int fd, unsigned long request, ...);
+        ''',
+        name: 'ioctl has glibc-style prototype'
+    ),
+    description: 'Is ioctl the glibc interface (rather than POSIX)'
+)
 
 if cc.has_function_attribute('fallthrough')
   conf.set('fallthrough', '__attribute__((__fallthrough__))')
diff --git a/test/ioctl/mock.c b/test/ioctl/mock.c
index e917244b..5d2ac94e 100644
--- a/test/ioctl/mock.c
+++ b/test/ioctl/mock.c
@@ -114,7 +114,11 @@ void end_mock_cmds(void)
 	} \
 })
 
+#ifdef HAVE_GLIBC_IOCTL
 int ioctl(int fd, unsigned long request, ...)
+#else
+int ioctl(int fd, int request, ...)
+#endif
 {
 	struct mock_cmds *mock_cmds;
 	bool result64;
@@ -141,7 +145,7 @@ int ioctl(int fd, unsigned long request, ...)
 		result64 = true;
 		break;
 	default:
-		fail("unexpected %s %lu", __func__, request);
+		fail("unexpected %s %lu", __func__, (unsigned long) request);
 	}
 	check(mock_cmds->remaining_cmds,
 	      "unexpected %s command", mock_cmds->name);