diff --git a/c/containers/dvector.c b/c/containers/dvector.c
index 8d8b72eec..dc42b9c85 100644
--- a/c/containers/dvector.c
+++ b/c/containers/dvector.c
@@ -4,8 +4,8 @@
 #include "containers/dvector.h"
 
 // ----------------------------------------------------------------
-dvector_t* dvector_alloc(int initial_capacity) {
-	int capacity = initial_capacity;
+dvector_t* dvector_alloc(unsigned long long initial_capacity) {
+	unsigned long long capacity = initial_capacity;
 	dvector_t* pdvector = mlr_malloc_or_die(sizeof(dvector_t));
 	pdvector->data     = mlr_malloc_or_die(capacity*sizeof(double));
 	pdvector->size     = 0;
@@ -26,7 +26,7 @@ void dvector_free(dvector_t* pdvector) {
 
 void dvector_append(dvector_t* pdvector, double value) {
 	if (pdvector->size >= pdvector->capacity) {
-		pdvector->capacity = (int)(pdvector->capacity * 2);
+		pdvector->capacity = (unsigned long long)(pdvector->capacity * 2);
 		pdvector->data = (double*)mlr_realloc_or_die(pdvector->data,
 			pdvector->capacity*sizeof(double));
 	}
diff --git a/c/containers/dvector.h b/c/containers/dvector.h
index 6b42044b3..c449f6f34 100644
--- a/c/containers/dvector.h
+++ b/c/containers/dvector.h
@@ -3,11 +3,11 @@
 
 typedef struct _dvector_t {
 	double* data;
-	int     size;
-	int     capacity;
+	unsigned long long size;
+	unsigned long long capacity;
 } dvector_t;
 
-dvector_t* dvector_alloc(int initial_capacity);
+dvector_t* dvector_alloc(unsigned long long initial_capacity);
 void dvector_free(dvector_t* pdvector);
 void dvector_append(dvector_t* pdvector, double value);
 
diff --git a/c/todo.txt b/c/todo.txt
index e54f00371..bb448b68e 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -44,6 +44,16 @@ TRI-SPLIT NULL
 
     mlr --opprint put '@sum[$a]=@sum[$a]+$x; filter false; end{dump}' ../data/small
 
+================================================================
+64-BIT CONTAINER SIZES
+
+k sllv
+* slls
+* rslls
+* sllmv
+* dvector & stats1/2 ...
+* top_keeper
+
 ================================================================
 MULTILEVEL EMIT: SPEC & IMPL