diff --git a/include/mruby/internal.h b/include/mruby/internal.h
index 89cd5d52b..7e643ce31 100644
--- a/include/mruby/internal.h
+++ b/include/mruby/internal.h
@@ -163,6 +163,9 @@ mrb_value mrb_str_inspect(mrb_state *mrb, mrb_value str);
 mrb_bool mrb_str_beg_len(mrb_int str_len, mrb_int *begp, mrb_int *lenp);
 mrb_value mrb_str_byte_subseq(mrb_state *mrb, mrb_value str, mrb_int beg, mrb_int len);
 mrb_value mrb_str_aref(mrb_state *mrb, mrb_value str, mrb_value idx, mrb_value len);
+mrb_bool mrb_strcasecmp_p(const char *s1, mrb_int len1, const char *s2, mrb_int len2);
+#define MRB_STR_CASECMP_P(str, lit) \
+  mrb_strcasecmp_p(RSTRING_PTR(str), RSTRING_LEN(str), lit, sizeof(lit"")-1)
 uint32_t mrb_byte_hash(const uint8_t*, mrb_int);
 uint32_t mrb_byte_hash_step(const uint8_t*, mrb_int, uint32_t);
 
diff --git a/mrbgems/mruby-encoding/src/encoding.c b/mrbgems/mruby-encoding/src/encoding.c
index 725dda4d5..4654e9fca 100644
--- a/mrbgems/mruby-encoding/src/encoding.c
+++ b/mrbgems/mruby-encoding/src/encoding.c
@@ -8,24 +8,6 @@
 #define ENC_BINARY     "BINARY"
 #define ENC_UTF8       "UTF-8"
 
-#define ENC_COMP_P(enc, enc_lit) \
-  casecmp_p(RSTRING_PTR(enc), RSTRING_LEN(enc), enc_lit, sizeof(enc_lit"")-1)
-
-static mrb_bool
-casecmp_p(const char *s1, mrb_int len1, const char *s2, mrb_int len2)
-{
-  if (len1 != len2) return FALSE;
-
-  const char *e1 = s1 + len1;
-  const char *e2 = s2 + len2;
-  while (s1 < e1 && s2 < e2) {
-    if (*s1 != *s2 && TOUPPER(*s1) != TOUPPER(*s2)) return FALSE;
-    s1++;
-    s2++;
-  }
-  return TRUE;
-}
-
 /*
  * call-seq:
  *   string.valid_encoding? -> true or false
@@ -104,11 +86,11 @@ str_force_encoding(mrb_state *mrb, mrb_value self)
   mrb_get_args(mrb, "S", &enc);
 
   struct RString *s = mrb_str_ptr(self);
-  if (ENC_COMP_P(enc, ENC_ASCII_8BIT) ||
-      ENC_COMP_P(enc, ENC_BINARY)) {
+  if (MRB_STR_CASECMP_P(enc, ENC_ASCII_8BIT) ||
+      MRB_STR_CASECMP_P(enc, ENC_BINARY)) {
     s->flags |= MRB_STR_BINARY;
   }
-  else if (ENC_COMP_P(enc, ENC_UTF8)) {
+  else if (MRB_STR_CASECMP_P(enc, ENC_UTF8)) {
     s->flags &= ~MRB_STR_BINARY;
   }
   else {
diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index 74dc1c7d1..45398b393 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -11,24 +11,6 @@
 #define ENC_BINARY     "BINARY"
 #define ENC_UTF8       "UTF-8"
 
-#define ENC_COMP_P(enc, enc_lit) \
-  casecmp_p(RSTRING_PTR(enc), RSTRING_LEN(enc), enc_lit, sizeof(enc_lit"")-1)
-
-static mrb_bool
-casecmp_p(const char *s1, mrb_int len1, const char *s2, mrb_int len2)
-{
-  if (len1 != len2) return FALSE;
-
-  const char *e1 = s1 + len1;
-  const char *e2 = s2 + len2;
-  while (s1 < e1 && s2 < e2) {
-    if (*s1 != *s2 && TOUPPER(*s1) != TOUPPER(*s2)) return FALSE;
-    s1++;
-    s2++;
-  }
-  return TRUE;
-}
-
 static mrb_value
 int_chr_binary(mrb_state *mrb, mrb_value num)
 {
@@ -873,12 +855,12 @@ int_chr(mrb_state *mrb, mrb_value num)
 
   mrb_get_args(mrb, "|S?", &enc, &enc_given);
   if (!enc_given ||
-      ENC_COMP_P(enc, ENC_ASCII_8BIT) ||
-      ENC_COMP_P(enc, ENC_BINARY)) {
+      MRB_STR_CASECMP_P(enc, ENC_ASCII_8BIT) ||
+      MRB_STR_CASECMP_P(enc, ENC_BINARY)) {
     return int_chr_binary(mrb, num);
   }
 #ifdef MRB_UTF8_STRING
-  else if (ENC_COMP_P(enc, ENC_UTF8)) {
+  else if (MRB_STR_CASECMP_P(enc, ENC_UTF8)) {
     return int_chr_utf8(mrb, num);
   }
 #endif
diff --git a/src/string.c b/src/string.c
index cf758e66a..0b5ed3bb1 100644
--- a/src/string.c
+++ b/src/string.c
@@ -50,6 +50,20 @@ str_check_length(mrb_state *mrb, mrb_int len)
 #endif
 }
 
+mrb_bool
+mrb_strcasecmp_p(const char *s1, mrb_int len1, const char *s2, mrb_int len2)
+{
+  if (len1 != len2) return FALSE;
+
+  const char *e1 = s1 + len1;
+  while (s1 < e1) {
+    if (*s1 != *s2 && TOUPPER(*s1) != TOUPPER(*s2)) return FALSE;
+    s1++;
+    s2++;
+  }
+  return TRUE;
+}
+
 static struct RString*
 str_init_normal_capa(mrb_state *mrb, struct RString *s,
                      const char *p, mrb_int len, mrb_int capa)