diff --git a/ext/openssl/ossl_asn1.c b/ext/openssl/ossl_asn1.c
index 0d3fa9ad15..71c452c88a 100644
--- a/ext/openssl/ossl_asn1.c
+++ b/ext/openssl/ossl_asn1.c
@@ -509,7 +509,8 @@ ossl_asn1_get_asn1type(VALUE obj)
     ASN1_TYPE *ret;
     VALUE value, rflag;
     void *ptr;
-    void (*free_func)();
+    typedef void free_func_type(void *);
+    free_func_type *free_func;
     int tag;
 
     tag = ossl_asn1_default_tag(obj);
@@ -522,16 +523,16 @@ ossl_asn1_get_asn1type(VALUE obj)
     case V_ASN1_INTEGER:         /* FALLTHROUGH */
     case V_ASN1_ENUMERATED:
 	ptr = obj_to_asn1int(value);
-	free_func = ASN1_INTEGER_free;
+	free_func = (free_func_type *)ASN1_INTEGER_free;
 	break;
     case V_ASN1_BIT_STRING:
         rflag = rb_attr_get(obj, sivUNUSED_BITS);
 	ptr = obj_to_asn1bstr(value, NUM2INT(rflag));
-	free_func = ASN1_BIT_STRING_free;
+	free_func = (free_func_type *)ASN1_BIT_STRING_free;
 	break;
     case V_ASN1_NULL:
 	ptr = obj_to_asn1null(value);
-	free_func = ASN1_NULL_free;
+	free_func = (free_func_type *)ASN1_NULL_free;
 	break;
     case V_ASN1_OCTET_STRING:    /* FALLTHROUGH */
     case V_ASN1_UTF8STRING:      /* FALLTHROUGH */
@@ -546,24 +547,24 @@ ossl_asn1_get_asn1type(VALUE obj)
     case V_ASN1_UNIVERSALSTRING: /* FALLTHROUGH */
     case V_ASN1_BMPSTRING:
 	ptr = obj_to_asn1str(value);
-	free_func = ASN1_STRING_free;
+	free_func = (free_func_type *)ASN1_STRING_free;
 	break;
     case V_ASN1_OBJECT:
 	ptr = obj_to_asn1obj(value);
-	free_func = ASN1_OBJECT_free;
+	free_func = (free_func_type *)ASN1_OBJECT_free;
 	break;
     case V_ASN1_UTCTIME:
 	ptr = obj_to_asn1utime(value);
-	free_func = ASN1_TIME_free;
+	free_func = (free_func_type *)ASN1_TIME_free;
 	break;
     case V_ASN1_GENERALIZEDTIME:
 	ptr = obj_to_asn1gtime(value);
-	free_func = ASN1_TIME_free;
+	free_func = (free_func_type *)ASN1_TIME_free;
 	break;
     case V_ASN1_SET:             /* FALLTHROUGH */
     case V_ASN1_SEQUENCE:
 	ptr = obj_to_asn1derstr(obj);
-	free_func = ASN1_STRING_free;
+	free_func = (free_func_type *)ASN1_STRING_free;
 	break;
     default:
 	ossl_raise(eASN1Error, "unsupported ASN.1 type");
diff --git a/ext/openssl/ossl_ssl.c b/ext/openssl/ossl_ssl.c
index af262d9f56..6e1a50fd6d 100644
--- a/ext/openssl/ossl_ssl.c
+++ b/ext/openssl/ossl_ssl.c
@@ -1662,7 +1662,7 @@ io_wait_readable(rb_io_t *fptr)
 }
 
 static VALUE
-ossl_start_ssl(VALUE self, int (*func)(), const char *funcname, VALUE opts)
+ossl_start_ssl(VALUE self, int (*func)(SSL *), const char *funcname, VALUE opts)
 {
     SSL *ssl;
     rb_io_t *fptr;