diff --git a/lib/drmtest.c b/lib/drmtest.c
index ed249f96..e1522b70 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -654,6 +654,8 @@ static enum {
 
 bool __igt_fixture(void)
 {
+	assert(!in_fixture);
+
 	if (igt_only_list_subtests())
 		return false;
 
@@ -666,11 +668,15 @@ bool __igt_fixture(void)
 
 void __igt_fixture_complete(void)
 {
+	assert(in_fixture);
+
 	in_fixture = false;
 }
 
 void __igt_fixture_end(void)
 {
+	assert(in_fixture);
+
 	in_fixture = false;
 	longjmp(igt_subtest_jmpbuf, 1);
 }