diff --git a/SStream.c b/SStream.c
index c90cf1a..1686d5d 100644
--- a/SStream.c
+++ b/SStream.c
@@ -28,6 +28,9 @@ void SStream_Init(SStream *ss)
 void SStream_concat0(SStream *ss, char *s)
 {
 #ifndef CAPSTONE_DIET
+	if (!ss || !s) {
+		return;
+	}
 	unsigned int len = (unsigned int) strlen(s);
 
 	memcpy(ss->buffer + ss->index, s, len);