diff --git a/embed.fnc b/embed.fnc
index 71efeda0dfc4..6af9f8a4fb3c 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1626,7 +1626,7 @@ Cp	|void	|init_stacks
 Cp	|void	|init_tm	|NN struct tm *ptm
 p	|void	|init_uniprops
 : Used in perly.y
-AMPRTbdp|char * |instr		|NN const char *big			\
+APRTdmp |char * |instr		|NN const char *big			\
 				|NN const char *little
 Adp	|U32	|intro_my
 ERXp	|Size_t |_inverse_folds |const UV cp				\
diff --git a/embed.h b/embed.h
index fdbcaa1db09b..d2e4576a26e0 100644
--- a/embed.h
+++ b/embed.h
@@ -307,6 +307,7 @@
 # define init_i18nl10n(a)                       Perl_init_i18nl10n(aTHX_ a)
 # define init_stacks()                          Perl_init_stacks(aTHX)
 # define init_tm(a)                             Perl_init_tm(aTHX_ a)
+# define instr                                  Perl_instr
 # define intro_my()                             Perl_intro_my(aTHX)
 # define isC9_STRICT_UTF8_CHAR                  Perl_isC9_STRICT_UTF8_CHAR
 # define isSTRICT_UTF8_CHAR                     Perl_isSTRICT_UTF8_CHAR
diff --git a/mathoms.c b/mathoms.c
index d6288c903deb..9592a4fe8750 100644
--- a/mathoms.c
+++ b/mathoms.c
@@ -802,17 +802,6 @@ Perl_utf8_to_uvuni(pTHX_ const U8 *s, STRLEN *retlen)
     return NATIVE_TO_UNI(valid_utf8_to_uvchr(s, retlen));
 }
 
-/* return ptr to little string in big string, NULL if not found */
-/* The original version of this routine was donated by Corey Satten. */
-
-char *
-Perl_instr(const char *big, const char *little)
-{
-    PERL_ARGS_ASSERT_INSTR;
-
-    return instr(big, little);
-}
-
 SV *
 Perl_newSVsv(pTHX_ SV *const old)
 {
diff --git a/proto.h b/proto.h
index 329c5ad318ef..b64d33d759fc 100644
--- a/proto.h
+++ b/proto.h
@@ -1797,6 +1797,11 @@ Perl_init_uniprops(pTHX)
         __attribute__visibility__("hidden");
 #define PERL_ARGS_ASSERT_INIT_UNIPROPS
 
+/* PERL_CALLCONV char *
+Perl_instr(const char *big, const char *little)
+        __attribute__warn_unused_result__
+        __attribute__pure__; */
+
 PERL_CALLCONV U32
 Perl_intro_my(pTHX);
 #define PERL_ARGS_ASSERT_INTRO_MY
@@ -5809,13 +5814,6 @@ PERL_CALLCONV SV **
 Perl_hv_store_flags(pTHX_ HV *hv, const char *key, I32 klen, SV *val, U32 hash, int flags);
 # define PERL_ARGS_ASSERT_HV_STORE_FLAGS
 
-PERL_CALLCONV char *
-Perl_instr(const char *big, const char *little)
-        __attribute__warn_unused_result__
-        __attribute__pure__;
-# define PERL_ARGS_ASSERT_INSTR                 \
-        assert(big); assert(little)
-
 PERL_CALLCONV STRLEN
 Perl_is_utf8_char_buf(const U8 *buf, const U8 *buf_end);
 # define PERL_ARGS_ASSERT_IS_UTF8_CHAR_BUF      \
diff --git a/util.h b/util.h
index 84d0e9f1c8d5..9ef5e38fcbb0 100644
--- a/util.h
+++ b/util.h
@@ -241,7 +241,7 @@ returning NULL if not found.  The terminating NUL bytes are not compared.
 */
 
 
-#define instr(haystack, needle) strstr((char *) haystack, (char *) needle)
+#define Perl_instr(haystack, needle) strstr((char *) haystack, (char *) needle)
 
 #ifdef HAS_MEMMEM
 #   define ninstr(big, bigend, little, lend)                                \