3 files changed, 14 insertions, 10 deletions
diff --git a/src/env.c b/src/env.c
index c37b6b6b..77682d6d 100644
--- a/src/env.c
+++ b/src/env.c
@@ -36,12 +36,8 @@ SERD_API
 SerdEnv*
 serd_env_new(const SerdNode* base_uri)
 {
-	SerdEnv* env = (SerdEnv*)malloc(sizeof(struct SerdEnvImpl));
-	env->prefixes      = NULL;
-	env->n_prefixes    = 0;
-	env->base_uri_node = SERD_NODE_NULL;
-	env->base_uri      = SERD_URI_NULL;
-	if (base_uri) {
+	SerdEnv* env = (SerdEnv*)calloc(sizeof(struct SerdEnvImpl), 1);
+	if (env && base_uri) {
 		serd_env_set_base_uri(env, base_uri);
 	}
 	return env;
@@ -76,6 +72,10 @@ SerdStatus
 serd_env_set_base_uri(SerdEnv*        env,
                       const SerdNode* uri_node)
 {
+	if (!env || !uri_node) {
+		return SERD_ERR_BAD_ARG;
+	}
+
 	// Resolve base URI and create a new node and URI for it
 	SerdURI  base_uri;
 	SerdNode base_uri_node = serd_node_new_uri_from_node(
diff --git a/src/node.c b/src/node.c
index 065ff875..a5305474 100644
--- a/src/node.c
+++ b/src/node.c
@@ -102,7 +102,7 @@ serd_node_new_uri_from_node(const SerdNode* uri_node,
                             const SerdURI*  base,
                             SerdURI*        out)
 {
-	return (uri_node->type == SERD_URI)
+	return (uri_node->type == SERD_URI && uri_node->buf)
 		? serd_node_new_uri_from_string(uri_node->buf, base, out)
 		: SERD_NODE_NULL;
 }
@@ -114,7 +114,11 @@ serd_node_new_uri_from_string(const uint8_t* str,
                               SerdURI*       out)
 {
 	if (!str || str[0] == '\0') {
-		return serd_node_new_uri(base, NULL, out);  // Empty URI => Base URI
+		if (base) {
+			return serd_node_new_uri(base, NULL, out);  // Empty URI => Base
+		} else {
+			return SERD_NODE_NULL;  // Nonsense
+		}
 	}
 	SerdURI uri;
 	serd_uri_parse(str, &uri);
@@ -340,7 +344,7 @@ SERD_API
 void
 serd_node_free(SerdNode* node)
 {
-	if (node->buf) {
+	if (node && node->buf) {
 		free((uint8_t*)node->buf);
 		node->buf = NULL;
 	}
diff --git a/src/uri.c b/src/uri.c
index 8f3bb997..6f7380b0 100644
--- a/src/uri.c
+++ b/src/uri.c
@@ -100,7 +100,7 @@ bool
 serd_uri_string_has_scheme(const uint8_t* utf8)
 {
 	// RFC3986: scheme ::= ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
-	if (!is_alpha(utf8[0])) {
+	if (!utf8 || !is_alpha(utf8[0])) {
 		return false;  // Invalid scheme initial character, URI is relative
 	}
 	for (uint8_t c; (c = *++utf8) != '\0';) {