diff --git a/RSA.xs b/RSA.xs
index 6bf64b3..270f17c 100644
--- a/RSA.xs
+++ b/RSA.xs
@@ -293,16 +293,24 @@ SV* extractBioString(BIO* p_stringBio)
 {
     SV* sv;
     char* datap;
-    long datasize = 0;
+    long datasize;
+    int error = 0;
 
-    CHECK_OPEN_SSL(BIO_flush(p_stringBio) == 1);
+    THROW(BIO_flush(p_stringBio) == 1);
 
     datasize = BIO_get_mem_data(p_stringBio, &datap);
+    THROW(datasize > 0);
+
     sv = newSVpv(datap, datasize);
 
-    CHECK_OPEN_SSL(BIO_set_close(p_stringBio, BIO_CLOSE) == 1);
+    BIO_set_close(p_stringBio, BIO_CLOSE);
     BIO_free(p_stringBio);
     return sv;
+
+    err:
+        BIO_free(p_stringBio);
+        CHECK_OPEN_SSL(0);
+        return NULL; /* unreachable, CHECK_OPEN_SSL croaks */
 }
 
 EVP_PKEY*  _load_rsa_key(SV* p_keyStringSv,