diff --git a/ext/openssl/ossl_asn1.c b/ext/openssl/ossl_asn1.c
index 502be1019f..1676defd0e 100644
--- a/ext/openssl/ossl_asn1.c
+++ b/ext/openssl/ossl_asn1.c
@@ -497,7 +497,7 @@ static VALUE class_tag_map;
 
 static int ossl_asn1_default_tag(VALUE obj);
 
-ASN1_TYPE*
+static ASN1_TYPE *
 ossl_asn1_get_asn1type(VALUE obj)
 {
     ASN1_TYPE *ret;
diff --git a/ext/openssl/ossl_asn1.h b/ext/openssl/ossl_asn1.h
index fae8762200..3a99400e18 100644
--- a/ext/openssl/ossl_asn1.h
+++ b/ext/openssl/ossl_asn1.h
@@ -57,8 +57,6 @@ extern VALUE cASN1Sequence, cASN1Set;                /* CONSTRUCTIVE      */
 
 extern VALUE cASN1EndOfContent;                      /* END OF CONTENT      */
 
-ASN1_TYPE *ossl_asn1_get_asn1type(VALUE);
-
 void Init_ossl_asn1(void);
 
 #endif