diff --git a/src/main/kotlin/com/beust/kobalt/api/ProjectProperties.kt b/src/main/kotlin/com/beust/kobalt/api/ProjectProperties.kt
index 88f263b3..0d7106eb 100644
--- a/src/main/kotlin/com/beust/kobalt/api/ProjectProperties.kt
+++ b/src/main/kotlin/com/beust/kobalt/api/ProjectProperties.kt
@@ -11,6 +11,10 @@ class ProjectProperties {
 
     fun get(key: String) = properties[key]
 
-    fun getString(key: String) = get(key) as String
+    fun getString(key: String) : String? {
+        val result = get(key)
+        return if (result != null) result as String
+            else null
+    }
 }