diff --git a/proto/tests.py b/proto/tests.py
index 4b3956bc..5dd6ebc6 100755
--- a/proto/tests.py
+++ b/proto/tests.py
@@ -273,7 +273,8 @@ def test_genc_ref():
     for f in ['issue103/top',
               'bug-gen-c-02/mbox_regs', 'bug-gen-c-02/fip_urv_regs',
               'issue67/repeatInRepeat', 'issue67/repeatInRepeatC',
-              'bug-same-label/same_label']:
+              'bug-same-label/same_label',
+              'features/blkprefix3', 'features/blkprefix4']:
         h_file = srcdir + f + '.h'
         cheby_file = srcdir + f + '.cheby'
         t = parse_ok(cheby_file)
diff --git a/testfiles/features/blkprefix3.h b/testfiles/features/blkprefix3.h
new file mode 100644
index 00000000..346e8884
--- /dev/null
+++ b/testfiles/features/blkprefix3.h
@@ -0,0 +1,51 @@
+#ifndef __CHEBY__BLKPREFIX3__H__
+#define __CHEBY__BLKPREFIX3__H__
+
+#include <stdint.h>
+
+#define BLKPREFIX3_SIZE 12 /* 0xc */
+
+/* (comment missing) */
+#define BLKPREFIX3_B1 0x0UL
+#define BLKPREFIX3_B1_SIZE 8 /* 0x8 */
+
+/* (comment missing) */
+#define BLKPREFIX3_B1_R2 0x0UL
+#define BLKPREFIX3_B1_R2_F1_MASK 0x7UL
+#define BLKPREFIX3_B1_R2_F1_SHIFT 0
+#define BLKPREFIX3_B1_R2_F2 0x10UL
+
+/* (comment missing) */
+#define BLKPREFIX3_B1_R3 0x4UL
+#define BLKPREFIX3_B1_R3_F1_MASK 0x7UL
+#define BLKPREFIX3_B1_R3_F1_SHIFT 0
+#define BLKPREFIX3_B1_R3_F2 0x10UL
+
+/* (comment missing) */
+#define BLKPREFIX3_B2 0x8UL
+#define BLKPREFIX3_B2_SIZE 4 /* 0x4 */
+
+/* (comment missing) */
+#define BLKPREFIX3_B2_R3 0x8UL
+#define BLKPREFIX3_B2_R3_F1_MASK 0x7UL
+#define BLKPREFIX3_B2_R3_F1_SHIFT 0
+
+#ifndef __ASSEMBLER__
+struct blkprefix3 {
+  /* [0x0]: BLOCK (comment missing) */
+  /* [0x0]: REG (rw) (comment missing) */
+  uint32_t r2;
+
+  /* [0x4]: BLOCK (comment missing) */
+  /* [0x0]: REG (rw) (comment missing) */
+  uint32_t r3;
+
+  /* [0x8]: BLOCK (comment missing) */
+  struct b2 {
+    /* [0x0]: REG (rw) (comment missing) */
+    uint32_t r3;
+  } b2;
+};
+#endif /* !__ASSEMBLER__*/
+
+#endif /* __CHEBY__BLKPREFIX3__H__ */