diff --git a/daemon/rtcp.c b/daemon/rtcp.c
index 4d0decf3e..7c197d2f4 100644
--- a/daemon/rtcp.c
+++ b/daemon/rtcp.c
@@ -774,13 +774,13 @@ INLINE int check_session_keys(struct crypto_context *c) {
 		goto error;
 
 	err = "Failed to generate SRTCP session keys";
-	str_init_len_assert(&s, c->session_key, c->params.crypto_suite->session_key_len);
+	s = STR_LEN_ASSERT(c->session_key, c->params.crypto_suite->session_key_len);
 	if (crypto_gen_session_key(c, &s, 0x03, SRTCP_R_LENGTH))
 		goto error;
-	str_init_len_assert(&s, c->session_auth_key, c->params.crypto_suite->srtcp_auth_key_len);
+	s = STR_LEN_ASSERT(c->session_auth_key, c->params.crypto_suite->srtcp_auth_key_len);
 	if (crypto_gen_session_key(c, &s, 0x04, SRTCP_R_LENGTH))
 		goto error;
-	str_init_len_assert(&s, c->session_salt, c->params.crypto_suite->session_salt_len);
+	s = STR_LEN_ASSERT(c->session_salt, c->params.crypto_suite->session_salt_len);
 	if (crypto_gen_session_key(c, &s, 0x05, SRTCP_R_LENGTH))
 		goto error;
 
diff --git a/daemon/rtp.c b/daemon/rtp.c
index c2fc9d3c1..b07a8bc25 100644
--- a/daemon/rtp.c
+++ b/daemon/rtp.c
@@ -23,13 +23,13 @@ INLINE int check_session_keys(struct crypto_context *c) {
 		goto error;
 
 	err = "Failed to generate SRTP session keys";
-	str_init_len_assert(&s, c->session_key, c->params.crypto_suite->session_key_len);
+	s = STR_LEN_ASSERT(c->session_key, c->params.crypto_suite->session_key_len);
 	if (crypto_gen_session_key(c, &s, 0x00, 6))
 		goto error;
-	str_init_len_assert(&s, c->session_auth_key, c->params.crypto_suite->srtp_auth_key_len);
+	s = STR_LEN_ASSERT(c->session_auth_key, c->params.crypto_suite->srtp_auth_key_len);
 	if (crypto_gen_session_key(c, &s, 0x01, 6))
 		goto error;
-	str_init_len_assert(&s, c->session_salt, c->params.crypto_suite->session_salt_len);
+	s = STR_LEN_ASSERT(c->session_salt, c->params.crypto_suite->session_salt_len);
 	if (crypto_gen_session_key(c, &s, 0x02, 6))
 		goto error;
 
diff --git a/lib/str.h b/lib/str.h
index 3fdabd15f..658ec165a 100644
--- a/lib/str.h
+++ b/lib/str.h
@@ -40,6 +40,7 @@ TYPED_GQUEUE(str, str)
 #define STR(s) ((str) { (char *) (s), (s) ? strlen(s) : 0 })
 #define STR_GS(s) ((str) { (s)->str, (s)->len })
 #define STR_LEN(s, len) ((str) { (char *) (s), len })
+#define STR_LEN_ASSERT(s, len) ({ assert(sizeof(s) >= len); (str) { (char *) (s), len }; })
 #define STR_INIT_DUP(s) ((str) { g_strdup(s), strlen(s) })
 #define STR_CONST_BUF(buf) ((str) { (char *) &buf, sizeof(buf) })
 
@@ -81,10 +82,6 @@ INLINE int str_casecmp_str(const str *a, const str *b);
 ACCESS(read_only, 1)
 ACCESS(read_only, 2)
 INLINE int str_cmp_str0(const str *a, const str *b);
-/* inits a str object from any binary string. returns out */
-__attribute__((nonnull(1, 2)))
-INLINE str *str_init_len_assert_len(str *out, char *s, size_t buflen, size_t len);
-#define str_init_len_assert(out, s, len) str_init_len_assert_len(out, s, sizeof(s), len)
 /* inits a str object from a regular string and duplicates the contents. returns out */
 __attribute__((nonnull(1)))
 ACCESS(write_only, 1)
@@ -298,11 +295,6 @@ INLINE int str_cmp_str0(const str *a, const str *b) {
 	}
 	return str_cmp_str(a, b);
 }
-INLINE str *str_init_len_assert_len(str *out, char *s, size_t buflen, size_t len) {
-	assert(buflen >= len);
-	*out = STR_LEN(s, len);
-	return out;
-}
 INLINE str *str_init_dup(str *out, const char *s) {
 	out->s = s ? g_strdup(s) : NULL;
 	out->len = s ? strlen(s) : 0;
diff --git a/t/aes-crypt.c b/t/aes-crypt.c
index 5a7e652b0..9f8be4c5a 100644
--- a/t/aes-crypt.c
+++ b/t/aes-crypt.c
@@ -183,13 +183,13 @@ extern void crypto_init_main(void);
 
 void check_session_keys(struct crypto_context *c, int i) {
 	str s;
-        str_init_len_assert(&s, c->session_key, c->params.crypto_suite->session_key_len);
+        s = STR_LEN_ASSERT(c->session_key, c->params.crypto_suite->session_key_len);
         if (crypto_gen_session_key(c, &s, i++, 6))
                 goto error;
-        str_init_len_assert(&s, c->session_auth_key, c->params.crypto_suite->srtp_auth_key_len);
+        s = STR_LEN_ASSERT(c->session_auth_key, c->params.crypto_suite->srtp_auth_key_len);
         if (crypto_gen_session_key(c, &s, i++, 6))
                 goto error;
-        str_init_len_assert(&s, c->session_salt, c->params.crypto_suite->session_salt_len);
+        s = STR_LEN_ASSERT(c->session_salt, c->params.crypto_suite->session_salt_len);
         if (crypto_gen_session_key(c, &s, i, 6))
                 goto error;