diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 2c607bf..520ce3f 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -1057,6 +1057,8 @@
 
 static char *envmatch (char * s1, char * s2)
 {
+	if (s1 == NULL || s2 == NULL)
+		return NULL;
 
 	while (*s1 == *s2++)
 		if (*s1++ == '=')