diff --git a/src/kits/app/Message.cpp b/src/kits/app/Message.cpp
index 435f9f1e28..ee38159012 100644
--- a/src/kits/app/Message.cpp
+++ b/src/kits/app/Message.cpp
@@ -1287,7 +1287,7 @@ DEFINE_LAZY_FIND_FUNCTION(const char*	, String)
 status_t 
 BMessage::AddString(const char* name, const char* string)
 {
-	return AddData(name, B_STRING_TYPE, string, strlen(string) + 1);
+	return AddData(name, B_STRING_TYPE, string, string ? strlen(string) + 1 : 0);
 }
 
 
diff --git a/src/kits/app/Message4.cpp b/src/kits/app/Message4.cpp
index 1fbe3ea72b..24b2fac1e3 100644
--- a/src/kits/app/Message4.cpp
+++ b/src/kits/app/Message4.cpp
@@ -2036,7 +2036,7 @@ DEFINE_LAZY_FIND_FUNCTION(double, Double, 0);
 status_t
 BMessage::AddString(const char *name, const char *string)
 {
-	return AddData(name, B_STRING_TYPE, string, strlen(string) + 1, false);
+	return AddData(name, B_STRING_TYPE, string, string ? strlen(string) + 1 : 0, false);
 }