diff --git a/README.md b/README.md
index 53e727f..ef5cf2b 100644
--- a/README.md
+++ b/README.md
@@ -501,19 +501,21 @@ SELECT * FROM (
 Use the `sparsevec` type to store sparse vectors
 
 ```sql
-CREATE TABLE items (id bigserial PRIMARY KEY, embedding sparsevec(10));
+CREATE TABLE items (id bigserial PRIMARY KEY, embedding sparsevec(5));
 ```
 
 Insert vectors
 
 ```sql
-INSERT INTO items (embedding) VALUES ('{0:1,1:2,2:3}/10'), ('{0:4,1:5,2:6}/10');
+INSERT INTO items (embedding) VALUES ('{1:1,3:2,5:3}/5'), ('{1:4,3:5,5:6}/5');
 ```
 
+Note: Indices start at 1 like SQL arrays
+
 Get the nearest neighbors by L2 distance
 
 ```sql
-SELECT * FROM items ORDER BY embedding <-> '{0:3,1:1,2:2}/10' LIMIT 5;
+SELECT * FROM items ORDER BY embedding <-> '{1:3,3:1,5:2}/5' LIMIT 5;
 ```
 
 ## Hybrid Search
diff --git a/src/sparsevec.c b/src/sparsevec.c
index 6e48f91..33551a7 100644
--- a/src/sparsevec.c
+++ b/src/sparsevec.c
@@ -89,15 +89,15 @@ CheckIndex(int32 *indices, int i, int dim)
 {
 	int32		index = indices[i];
 
-	if (index < 0)
+	if (index < 1)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATA_EXCEPTION),
-				 errmsg("index must not be negative")));
+				 errmsg("index must be greater than zero")));
 
-	if (index >= dim)
+	if (index > dim)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATA_EXCEPTION),
-				 errmsg("index must be less than dimensions")));
+				 errmsg("index must be less than or equal to dimensions")));
 
 	if (i > 0)
 	{
@@ -245,7 +245,7 @@ sparsevec_in(PG_FUNCTION_ARGS)
 					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
 					 errmsg("invalid input syntax for type sparsevec: \"%s\"", lit)));
 
-		if (errno == ERANGE || index < 0 || index > INT_MAX)
+		if (errno == ERANGE || index < 1 || index > INT_MAX)
 			ereport(ERROR,
 					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 					 errmsg("index \"%ld\" is out of range for type sparsevec", index)));
diff --git a/src/vector.c b/src/vector.c
index 1f5ec89..31e7386 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -1244,7 +1244,7 @@ sparsevec_to_vector(PG_FUNCTION_ARGS)
 
 	result = InitVector(dim);
 	for (int i = 0; i < svec->nnz; i++)
-		result->x[svec->indices[i]] = values[i];
+		result->x[svec->indices[i] - 1] = values[i];
 
 	PG_RETURN_POINTER(result);
 }
diff --git a/test/expected/hnsw_sparsevec_cosine.out b/test/expected/hnsw_sparsevec_cosine.out
index 778415e..8645580 100644
--- a/test/expected/hnsw_sparsevec_cosine.out
+++ b/test/expected/hnsw_sparsevec_cosine.out
@@ -1,14 +1,14 @@
 SET enable_seqscan = off;
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_cosine_ops);
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
-SELECT * FROM t ORDER BY val <=> '{0:3,1:3,2:3}/3';
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
+SELECT * FROM t ORDER BY val <=> '{1:3,2:3,3:3}/3';
        val       
 -----------------
- {0:1,1:1,2:1}/3
- {0:1,1:2,2:3}/3
- {0:1,1:2,2:4}/3
+ {1:1,2:1,3:1}/3
+ {1:1,2:2,3:3}/3
+ {1:1,2:2,3:4}/3
 (3 rows)
 
 SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <=> '{}/3') t2;
diff --git a/test/expected/hnsw_sparsevec_ip.out b/test/expected/hnsw_sparsevec_ip.out
index 1c303f0..bfc212b 100644
--- a/test/expected/hnsw_sparsevec_ip.out
+++ b/test/expected/hnsw_sparsevec_ip.out
@@ -1,14 +1,14 @@
 SET enable_seqscan = off;
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_ip_ops);
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
-SELECT * FROM t ORDER BY val <#> '{0:3,1:3,2:3}/3';
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
+SELECT * FROM t ORDER BY val <#> '{1:3,2:3,3:3}/3';
        val       
 -----------------
- {0:1,1:2,2:4}/3
- {0:1,1:2,2:3}/3
- {0:1,1:1,2:1}/3
+ {1:1,2:2,3:4}/3
+ {1:1,2:2,3:3}/3
+ {1:1,2:1,3:1}/3
  {}/3
 (4 rows)
 
diff --git a/test/expected/hnsw_sparsevec_l2.out b/test/expected/hnsw_sparsevec_l2.out
index adc5cfd..f474871 100644
--- a/test/expected/hnsw_sparsevec_l2.out
+++ b/test/expected/hnsw_sparsevec_l2.out
@@ -1,14 +1,14 @@
 SET enable_seqscan = off;
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_l2_ops);
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
-SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}/3';
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
+SELECT * FROM t ORDER BY val <-> '{1:3,2:3,3:3}/3';
        val       
 -----------------
- {0:1,1:2,2:3}/3
- {0:1,1:2,2:4}/3
- {0:1,1:1,2:1}/3
+ {1:1,2:2,3:3}/3
+ {1:1,2:2,3:4}/3
+ {1:1,2:1,3:1}/3
  {}/3
 (4 rows)
 
@@ -25,7 +25,7 @@ SELECT COUNT(*) FROM t;
 (1 row)
 
 TRUNCATE t;
-SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}/3';
+SELECT * FROM t ORDER BY val <-> '{1:3,2:3,3:3}/3';
  val 
 -----
 (0 rows)
diff --git a/test/expected/sparsevec_functions.out b/test/expected/sparsevec_functions.out
index 07117d8..3633060 100644
--- a/test/expected/sparsevec_functions.out
+++ b/test/expected/sparsevec_functions.out
@@ -1,52 +1,52 @@
-SELECT l2_distance('{}/2'::sparsevec, '{0:3,1:4}/2');
+SELECT l2_distance('{}/2'::sparsevec, '{1:3,2:4}/2');
  l2_distance 
 -------------
            5
 (1 row)
 
-SELECT l2_distance('{}/2'::sparsevec, '{1:1}/2');
+SELECT l2_distance('{}/2'::sparsevec, '{2:1}/2');
  l2_distance 
 -------------
            1
 (1 row)
 
-SELECT '{}/2'::sparsevec <-> '{0:3,1:4}/2';
+SELECT '{}/2'::sparsevec <-> '{1:3,2:4}/2';
  ?column? 
 ----------
         5
 (1 row)
 
-SELECT inner_product('{0:1,1:2}/2'::sparsevec, '{0:2,1:4}/2');
+SELECT inner_product('{1:1,2:2}/2'::sparsevec, '{1:2,2:4}/2');
  inner_product 
 ---------------
             10
 (1 row)
 
-SELECT sparsevec_negative_inner_product('{0:1,1:2}/2', '{0:2,1:4}/2');
+SELECT sparsevec_negative_inner_product('{1:1,2:2}/2', '{1:2,2:4}/2');
  sparsevec_negative_inner_product 
 ----------------------------------
                               -10
 (1 row)
 
-SELECT cosine_distance('{0:1,1:2}/2'::sparsevec, '{0:2,1:4}/2');
+SELECT cosine_distance('{1:1,2:2}/2'::sparsevec, '{1:2,2:4}/2');
  cosine_distance 
 -----------------
                0
 (1 row)
 
-SELECT cosine_distance('{0:1,1:2}/2'::sparsevec, '{}/2');
+SELECT cosine_distance('{1:1,2:2}/2'::sparsevec, '{}/2');
  cosine_distance 
 -----------------
              NaN
 (1 row)
 
-SELECT cosine_distance('{0:1,1:1}/2'::sparsevec, '{0:-1,1:-1}/2');
+SELECT cosine_distance('{1:1,2:1}/2'::sparsevec, '{1:-1,2:-1}/2');
  cosine_distance 
 -----------------
                2
 (1 row)
 
-SELECT cosine_distance('{0:1}/2'::sparsevec, '{1:2}/2');
+SELECT cosine_distance('{1:2}/2'::sparsevec, '{2:2}/2');
  cosine_distance 
 -----------------
                1
@@ -58,5 +58,5 @@ SELECT cosine_distance('{}/1'::sparsevec, '{}/1');
              NaN
 (1 row)
 
-SELECT cosine_distance('{0:1}/2'::sparsevec, '{0:1}/3');
+SELECT cosine_distance('{1:2}/2'::sparsevec, '{1:1}/3');
 ERROR:  different sparsevec dimensions 2 and 3
diff --git a/test/expected/sparsevec_input.out b/test/expected/sparsevec_input.out
index bd2faf5..c25b852 100644
--- a/test/expected/sparsevec_input.out
+++ b/test/expected/sparsevec_input.out
@@ -1,22 +1,22 @@
-SELECT '{0:1.5,2:3.5}/5'::sparsevec;
+SELECT '{1:1.5,3:3.5}/5'::sparsevec;
     sparsevec    
 -----------------
- {0:1.5,2:3.5}/5
+ {1:1.5,3:3.5}/5
 (1 row)
 
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector;
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector;
      vector      
 -----------------
  [1.5,0,3.5,0,0]
 (1 row)
 
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector(5);
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector(5);
      vector      
 -----------------
  [1.5,0,3.5,0,0]
 (1 row)
 
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector(4);
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector(4);
 ERROR:  expected 4 dimensions, not 5
 SELECT '[0,1.5,0,3.5,0]'::vector::sparsevec;
     sparsevec    
@@ -24,15 +24,15 @@ SELECT '[0,1.5,0,3.5,0]'::vector::sparsevec;
  {1:1.5,3:3.5}/5
 (1 row)
 
-SELECT '{0:0,1:1,2:0}/3'::sparsevec;
+SELECT '{1:0,2:1,3:0}/3'::sparsevec;
  sparsevec 
 -----------
- {1:1}/3
+ {2:1}/3
 (1 row)
 
-SELECT '{1:1,0:1}/2'::sparsevec;
+SELECT '{2:1,1:1}/2'::sparsevec;
 ERROR:  indexes must be in ascending order
-LINE 1: SELECT '{1:1,0:1}/2'::sparsevec;
+LINE 1: SELECT '{2:1,1:1}/2'::sparsevec;
                ^
 SELECT '{}/5'::sparsevec;
  sparsevec 
@@ -50,13 +50,13 @@ LINE 1: SELECT '{}/100001'::sparsevec;
                ^
 SELECT '{}/16001'::sparsevec::vector;
 ERROR:  vector cannot have more than 16000 dimensions
-SELECT '{-1:1}/1'::sparsevec;
-ERROR:  index "-1" is out of range for type sparsevec
-LINE 1: SELECT '{-1:1}/1'::sparsevec;
+SELECT '{0:1}/1'::sparsevec;
+ERROR:  index "0" is out of range for type sparsevec
+LINE 1: SELECT '{0:1}/1'::sparsevec;
                ^
-SELECT '{1:1}/1'::sparsevec;
-ERROR:  index must be less than dimensions
-LINE 1: SELECT '{1:1}/1'::sparsevec;
+SELECT '{2:1}/1'::sparsevec;
+ERROR:  index must be less than or equal to dimensions
+LINE 1: SELECT '{2:1}/1'::sparsevec;
                ^
 SELECT '{}/1'::sparsevec(2);
 ERROR:  expected 2 dimensions, not 1
diff --git a/test/sql/hnsw_sparsevec_cosine.sql b/test/sql/hnsw_sparsevec_cosine.sql
index 685423c..2ba1c1e 100644
--- a/test/sql/hnsw_sparsevec_cosine.sql
+++ b/test/sql/hnsw_sparsevec_cosine.sql
@@ -1,12 +1,12 @@
 SET enable_seqscan = off;
 
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_cosine_ops);
 
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
 
-SELECT * FROM t ORDER BY val <=> '{0:3,1:3,2:3}/3';
+SELECT * FROM t ORDER BY val <=> '{1:3,2:3,3:3}/3';
 SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <=> '{}/3') t2;
 SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <=> (SELECT NULL::sparsevec)) t2;
 
diff --git a/test/sql/hnsw_sparsevec_ip.sql b/test/sql/hnsw_sparsevec_ip.sql
index 1888d9c..1fc8449 100644
--- a/test/sql/hnsw_sparsevec_ip.sql
+++ b/test/sql/hnsw_sparsevec_ip.sql
@@ -1,12 +1,12 @@
 SET enable_seqscan = off;
 
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_ip_ops);
 
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
 
-SELECT * FROM t ORDER BY val <#> '{0:3,1:3,2:3}/3';
+SELECT * FROM t ORDER BY val <#> '{1:3,2:3,3:3}/3';
 SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <#> (SELECT NULL::sparsevec)) t2;
 
 DROP TABLE t;
diff --git a/test/sql/hnsw_sparsevec_l2.sql b/test/sql/hnsw_sparsevec_l2.sql
index b472607..9163c47 100644
--- a/test/sql/hnsw_sparsevec_l2.sql
+++ b/test/sql/hnsw_sparsevec_l2.sql
@@ -1,17 +1,17 @@
 SET enable_seqscan = off;
 
 CREATE TABLE t (val sparsevec(3));
-INSERT INTO t (val) VALUES ('{}/3'), ('{0:1,1:2,2:3}/3'), ('{0:1,1:1,2:1}/3'), (NULL);
+INSERT INTO t (val) VALUES ('{}/3'), ('{1:1,2:2,3:3}/3'), ('{1:1,2:1,3:1}/3'), (NULL);
 CREATE INDEX ON t USING hnsw (val sparsevec_l2_ops);
 
-INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}/3');
+INSERT INTO t (val) VALUES ('{1:1,2:2,3:4}/3');
 
-SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}/3';
+SELECT * FROM t ORDER BY val <-> '{1:3,2:3,3:3}/3';
 SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <-> (SELECT NULL::sparsevec)) t2;
 SELECT COUNT(*) FROM t;
 
 TRUNCATE t;
-SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}/3';
+SELECT * FROM t ORDER BY val <-> '{1:3,2:3,3:3}/3';
 
 DROP TABLE t;
 
diff --git a/test/sql/sparsevec_functions.sql b/test/sql/sparsevec_functions.sql
index 86f7990..57eca71 100644
--- a/test/sql/sparsevec_functions.sql
+++ b/test/sql/sparsevec_functions.sql
@@ -1,13 +1,13 @@
-SELECT l2_distance('{}/2'::sparsevec, '{0:3,1:4}/2');
-SELECT l2_distance('{}/2'::sparsevec, '{1:1}/2');
-SELECT '{}/2'::sparsevec <-> '{0:3,1:4}/2';
+SELECT l2_distance('{}/2'::sparsevec, '{1:3,2:4}/2');
+SELECT l2_distance('{}/2'::sparsevec, '{2:1}/2');
+SELECT '{}/2'::sparsevec <-> '{1:3,2:4}/2';
 
-SELECT inner_product('{0:1,1:2}/2'::sparsevec, '{0:2,1:4}/2');
-SELECT sparsevec_negative_inner_product('{0:1,1:2}/2', '{0:2,1:4}/2');
+SELECT inner_product('{1:1,2:2}/2'::sparsevec, '{1:2,2:4}/2');
+SELECT sparsevec_negative_inner_product('{1:1,2:2}/2', '{1:2,2:4}/2');
 
-SELECT cosine_distance('{0:1,1:2}/2'::sparsevec, '{0:2,1:4}/2');
-SELECT cosine_distance('{0:1,1:2}/2'::sparsevec, '{}/2');
-SELECT cosine_distance('{0:1,1:1}/2'::sparsevec, '{0:-1,1:-1}/2');
-SELECT cosine_distance('{0:1}/2'::sparsevec, '{1:2}/2');
+SELECT cosine_distance('{1:1,2:2}/2'::sparsevec, '{1:2,2:4}/2');
+SELECT cosine_distance('{1:1,2:2}/2'::sparsevec, '{}/2');
+SELECT cosine_distance('{1:1,2:1}/2'::sparsevec, '{1:-1,2:-1}/2');
+SELECT cosine_distance('{1:2}/2'::sparsevec, '{2:2}/2');
 SELECT cosine_distance('{}/1'::sparsevec, '{}/1');
-SELECT cosine_distance('{0:1}/2'::sparsevec, '{0:1}/3');
+SELECT cosine_distance('{1:2}/2'::sparsevec, '{1:1}/3');
diff --git a/test/sql/sparsevec_input.sql b/test/sql/sparsevec_input.sql
index 1fdfd88..757afc0 100644
--- a/test/sql/sparsevec_input.sql
+++ b/test/sql/sparsevec_input.sql
@@ -1,19 +1,19 @@
-SELECT '{0:1.5,2:3.5}/5'::sparsevec;
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector;
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector(5);
-SELECT '{0:1.5,2:3.5}/5'::sparsevec::vector(4);
+SELECT '{1:1.5,3:3.5}/5'::sparsevec;
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector;
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector(5);
+SELECT '{1:1.5,3:3.5}/5'::sparsevec::vector(4);
 SELECT '[0,1.5,0,3.5,0]'::vector::sparsevec;
 
-SELECT '{0:0,1:1,2:0}/3'::sparsevec;
+SELECT '{1:0,2:1,3:0}/3'::sparsevec;
 
-SELECT '{1:1,0:1}/2'::sparsevec;
+SELECT '{2:1,1:1}/2'::sparsevec;
 
 SELECT '{}/5'::sparsevec;
 SELECT '{}/-1'::sparsevec;
 SELECT '{}/100001'::sparsevec;
 SELECT '{}/16001'::sparsevec::vector;
 
-SELECT '{-1:1}/1'::sparsevec;
-SELECT '{1:1}/1'::sparsevec;
+SELECT '{0:1}/1'::sparsevec;
+SELECT '{2:1}/1'::sparsevec;
 
 SELECT '{}/1'::sparsevec(2);