diff --git a/spa/include/spa/utils/json.h b/spa/include/spa/utils/json.h
index 73cad7f59..19093169b 100644
--- a/spa/include/spa/utils/json.h
+++ b/spa/include/spa/utils/json.h
@@ -240,6 +240,8 @@ static inline bool spa_json_is_null(const char *val, int len)
 static inline int spa_json_parse_float(const char *val, int len, float *result)
 {
 	char *end;
+	if (strspn(val, "+-0123456789.Ee") < (size_t)len)
+		return 0;
 	*result = spa_strtof(val, &end);
 	return len > 0 && end == val + len;
 }
diff --git a/test/test-spa-json.c b/test/test-spa-json.c
index 8187787fd..9ca5bfbe2 100644
--- a/test/test-spa-json.c
+++ b/test/test-spa-json.c
@@ -86,7 +86,7 @@ static void expect_float(struct spa_json *it, float val)
 {
 	const char *value;
 	int len;
-	float f;
+	float f = 0.0f;
 	pwtest_int_gt((len = spa_json_next(it, &value)), 0);
 	check_type(TYPE_FLOAT, value, len);
 	pwtest_int_gt(spa_json_parse_float(value, len, &f), 0);