diff --git a/src/main/java/millions/Stock.java b/src/main/java/millions/Stock.java
index 41a3ead..632c4b7 100644
--- a/src/main/java/millions/Stock.java
+++ b/src/main/java/millions/Stock.java
@@ -13,12 +13,18 @@ public Stock(String symbol, String company, List<BigDecimal> prices) {
     this.symbol = symbol;
     this.company = company;
     this.prices = new ArrayList<>(prices);
+
+    if (symbol == null || symbol.isBlank()) {
+      throw new IllegalArgumentException("Symbol cannot be null or blank");
+    }
+
+    if (company == null || company.isBlank()) {
+      throw new IllegalArgumentException("Company cannot be null or blank");
+    }
   }
 
   public Stock(String symbol, String company, BigDecimal initialPrice) {
-    this.symbol = symbol;
-    this.company = company;
-    this.prices = new ArrayList<>(List.of(initialPrice));
+    this(symbol, company, new ArrayList<>(List.of(initialPrice)));
   }
 
   public String getSymbol() {