diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 9640687..30261a5 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -4430,7 +4430,7 @@
     }
 #if defined(MBEDTLS_CHACHA20_C)
     else
-    if( alg == PSA_ALG_CHACHA20 )
+    if( alg == PSA_ALG_STREAM_CIPHER && slot->attr.type == PSA_KEY_TYPE_CHACHA20 )
         operation->iv_size = 12;
 #endif