Index: src/OFDataArray.m
==================================================================
--- src/OFDataArray.m
+++ src/OFDataArray.m
@@ -289,11 +289,11 @@
 
 - (void)addNItems: (size_t)nItems
        fromCArray: (const void*)cArray
 	  atIndex: (size_t)index
 {
-	if (nItems > SIZE_MAX - count)
+	if (nItems > SIZE_MAX - count || index > count)
 		@throw [OFOutOfRangeException exceptionWithClass: isa];
 
 	data = [self resizeMemory: data
 			 toNItems: count + nItems
 			   ofSize: itemSize];