diff --git a/library/cipher.c b/library/cipher.c
index 63eaba8..7e6d0e0 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -545,9 +545,9 @@
 #if defined(MBEDTLS_GCM_C)
     if( ctx->cipher_info->mode == MBEDTLS_MODE_GCM )
     {
-        *olen = ilen;
-        return( mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx, ilen, input,
-                                    output ) );
+        return( mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx,
+                                    input, ilen,
+                                    output, ilen, olen ) );
     }
 #endif