1 files changed, 5 insertions, 0 deletions
diff --git a/src/sgr.c b/src/sgr.c
index 4017b72..b768e96 100644
--- a/src/sgr.c
+++ b/src/sgr.c
@@ -21,6 +21,7 @@
 
 #include "sgr.h"
 
+#include <assert.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -57,6 +58,10 @@ sgr(unsigned char *param, png_colorp fg, png_colorp bg)
 	unsigned char *p;
 	int            i;
 
+	assert(param);
+	assert(fg);
+	assert(bg);
+
 	end = 0;
 	for (p = param; param; ++param) {
 		if (*param == ';' || *param == ':' || *param == '\0') {