diff --git a/keccak_tiny.nim b/keccak_tiny.nim
index 28293a9..2a414ca 100644
--- a/keccak_tiny.nim
+++ b/keccak_tiny.nim
@@ -1,5 +1,5 @@
 {.compile: "keccak-tiny/keccak-tiny.c".}
-when defined(c):
+when not defined(cpp) or defined(objc) or defined(js):
     {.passC: "-std=c99".}
 
 import