diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 187a8c0..eeb8545 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -165,8 +165,15 @@ static char *fw_string_blank(char *s, int noblank)
 char *fw_getenv (char *name)
 {
 	char *env, *nxt;
+	for (nxt = env = environment.data; !(*nxt); ++nxt) {
+		if (nxt >= &environment.data[ENV_SIZE]) {
+			fprintf (stderr, "## Error: "
+				"environment is empty\n");
+			return NULL;
+		}
+	}

-	for (env = environment.data; *env; env = nxt + 1) {
+	for (env = nxt; *env; env = nxt + 1) {
 		char *val;

 		for (nxt = env; *nxt; ++nxt) {
@@ -191,8 +198,15 @@ char *fw_getenv (char *name)
 char *fw_getdefenv(char *name)
 {
 	char *env, *nxt;
+	for (nxt = env = default_environment; !(*nxt); ++nxt) {
+		if (nxt >= &default_environment[ENV_SIZE]) {
+			fprintf (stderr, "## Error: "
+				"default environment is empty\n");
+			return NULL;
+		}
+	}

-	for (env = default_environment; *env; env = nxt + 1) {
+	for (env = nxt; *env; env = nxt + 1) {
 		char *val;

 		for (nxt = env; *nxt; ++nxt) {
@@ -267,7 +281,14 @@ int fw_printenv (int argc, char *argv[])
 		return -1;

 	if (argc == 1) {		/* Print all env variables  */
-		for (env = environment.data; *env; env = nxt + 1) {
+		for (nxt = env = environment.data; !(*nxt); ++nxt) {
+			if (nxt >= &environment.data[ENV_SIZE]) {
+				fprintf (stderr, "## Error: "
+					"environment is empty\n");
+				return -1;
+			}
+		}
+		for (env = nxt; *env; env = nxt + 1) {
 			for (nxt = env; *nxt; ++nxt) {
 				if (nxt >= &environment.data[ENV_SIZE]) {
 					fprintf (stderr, "## Error: "
@@ -298,8 +319,14 @@ int fw_printenv (int argc, char *argv[])
 		char *name = argv[i];
 		char *val = NULL;

-		for (env = environment.data; *env; env = nxt + 1) {
-
+		for (nxt = env = environment.data; !(*nxt); ++nxt) {
+			if (nxt >= &environment.data[ENV_SIZE]) {
+				fprintf (stderr, "## Error: "
+					"environment is empty\n");
+				return -1;
+			}
+		}
+		for (env = nxt; *env; env = nxt + 1) {
 			for (nxt = env; *nxt; ++nxt) {
 				if (nxt >= &environment.data[ENV_SIZE]) {
 					fprintf (stderr, "## Error: "
@@ -369,7 +396,14 @@ int fw_env_write(char *name, char *value)
 	/*
 	 * search if variable with this name already exists
 	 */
-	for (nxt = env = environment.data; *env; env = nxt + 1) {
+	for (nxt = env = environment.data; !(*nxt); ++nxt) {
+		if (nxt >= &environment.data[ENV_SIZE]) {
+			fprintf (stderr, "## Error: "
+				"environment is empty\n");
+			return -1;
+		}
+	}
+	for (env = nxt; *env; env = nxt + 1) {
 		for (nxt = env; *nxt; ++nxt) {
 			if (nxt >= &environment.data[ENV_SIZE]) {
 				fprintf(stderr, "## Error: "