4 files changed, 37 insertions, 12 deletions
diff --git a/compile.c b/compile.c
index 0bb6c59e6c..51d6f1be01 100644
--- a/compile.c
+++ b/compile.c
@@ -7985,7 +7985,11 @@ struct ibf_id_entry {
 	ibf_id_enc_ascii,
 	ibf_id_enc_utf8,
 	ibf_id_enc_other
-    } enc : 2;
+    } enc
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+    : 2
+#endif
+    ;
     char body[1];
 };
 
diff --git a/method.h b/method.h
index dc430401a7..7c1ce3b8b3 100644
--- a/method.h
+++ b/method.h
@@ -32,10 +32,16 @@ typedef enum {
     METHOD_VISI_MASK = 0x03
 } rb_method_visibility_t;
 
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+#define bits_t rb_method_visibility_t
+#else
+#define bits_t unsigned int
+#endif
 typedef struct rb_scope_visi_struct {
-    rb_method_visibility_t method_visi : 3;
+    bits_t method_visi : 3;
     unsigned int module_func : 1;
 } rb_scope_visibility_t;
+#undef bits_t
 
 /*! CREF (Class REFerence) */
 typedef struct rb_cref_struct {
diff --git a/time.c b/time.c
index e0a95097bd..fca9d37b89 100644
--- a/time.c
+++ b/time.c
@@ -1596,12 +1596,18 @@ localtimew(wideval_t timew, struct vtm *result)
     return result;
 }
 
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+#define bits_t uint8_t
+#else
+#define bits_t unsigned int
+#endif
 PACKED_STRUCT_UNALIGNED(struct time_object {
     wideval_t timew; /* time_t value * TIME_SCALE.  possibly Rational. */
     struct vtm vtm;
-    uint8_t gmt:3; /* 0:localtime 1:utc 2:fixoff 3:init */
-    uint8_t tm_got:1;
+    bits_t gmt:3; /* 0:localtime 1:utc 2:fixoff 3:init */
+    bits_t tm_got:1;
 });
+#undef bits_t
 
 #define GetTimeval(obj, tobj) ((tobj) = get_timeval(obj))
 #define GetNewTimeval(obj, tobj) ((tobj) = get_new_timeval(obj))
diff --git a/timev.h b/timev.h
index 3947477630..29e92b558b 100644
--- a/timev.h
+++ b/timev.h
@@ -1,20 +1,29 @@
 #ifndef RUBY_TIMEV_H
 #define RUBY_TIMEV_H
 
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
+#define bits8_t uint8_t
+#define bits16_t uint16_t
+#else
+#define bits8_t unsigned int
+#define bits16_t unsigned int
+#endif
 PACKED_STRUCT_UNALIGNED(struct vtm {
     VALUE year; /* 2000 for example.  Integer. */
     VALUE subsecx; /* 0 <= subsecx < TIME_SCALE.  possibly Rational. */
     VALUE utc_offset; /* -3600 as -01:00 for example.  possibly Rational. */
     const char *zone; /* "JST", "EST", "EDT", etc. */
-    uint16_t yday:9; /* 1..366 */
-    uint8_t mon:4; /* 1..12 */
-    uint8_t mday:5; /* 1..31 */
-    uint8_t hour:5; /* 0..23 */
-    uint8_t min:6; /* 0..59 */
-    uint8_t sec:6; /* 0..60 */
-    uint8_t wday:3; /* 0:Sunday, 1:Monday, ..., 6:Saturday 7:init */
-    uint8_t isdst:2; /* 0:StandardTime 1:DayLightSavingTime 3:init */
+    bits16_t yday:9; /* 1..366 */
+    bits8_t mon:4; /* 1..12 */
+    bits8_t mday:5; /* 1..31 */
+    bits8_t hour:5; /* 0..23 */
+    bits8_t min:6; /* 0..59 */
+    bits8_t sec:6; /* 0..60 */
+    bits8_t wday:3; /* 0:Sunday, 1:Monday, ..., 6:Saturday 7:init */
+    bits8_t isdst:2; /* 0:StandardTime 1:DayLightSavingTime 3:init */
 });
+#undef bits8_t
+#undef bits16_t
 
 #define TIME_SCALE 1000000000