diff --git a/lib/src/store/numeric_encoder.rs b/lib/src/store/numeric_encoder.rs
index fed6e981..80a91bee 100644
--- a/lib/src/store/numeric_encoder.rs
+++ b/lib/src/store/numeric_encoder.rs
@@ -12,7 +12,7 @@ use siphasher::sip128::{Hasher128, SipHasher24};
 use std::collections::HashMap;
 use std::hash::Hash;
 use std::hash::Hasher;
-use std::io::{Cursor, Read};
+use std::io::{Cursor, Error as IoError, ErrorKind, Read, Result as IoResult};
 use std::mem::size_of;
 use std::str;
 
@@ -607,17 +607,17 @@ impl From<&Quad> for EncodedQuad {
 }
 
 pub trait TermReader {
-    fn read_term(&mut self) -> Result<EncodedTerm>;
-    fn read_spog_quad(&mut self) -> Result<EncodedQuad>;
-    fn read_posg_quad(&mut self) -> Result<EncodedQuad>;
-    fn read_ospg_quad(&mut self) -> Result<EncodedQuad>;
-    fn read_gspo_quad(&mut self) -> Result<EncodedQuad>;
-    fn read_gpos_quad(&mut self) -> Result<EncodedQuad>;
-    fn read_gosp_quad(&mut self) -> Result<EncodedQuad>;
+    fn read_term(&mut self) -> IoResult<EncodedTerm>;
+    fn read_spog_quad(&mut self) -> IoResult<EncodedQuad>;
+    fn read_posg_quad(&mut self) -> IoResult<EncodedQuad>;
+    fn read_ospg_quad(&mut self) -> IoResult<EncodedQuad>;
+    fn read_gspo_quad(&mut self) -> IoResult<EncodedQuad>;
+    fn read_gpos_quad(&mut self) -> IoResult<EncodedQuad>;
+    fn read_gosp_quad(&mut self) -> IoResult<EncodedQuad>;
 }
 
 impl<R: Read> TermReader for R {
-    fn read_term(&mut self) -> Result<EncodedTerm> {
+    fn read_term(&mut self) -> IoResult<EncodedTerm> {
         let mut type_buffer = [0];
         self.read_exact(&mut type_buffer)?;
         match type_buffer[0] {
@@ -730,11 +730,14 @@ impl<R: Read> TermReader for R {
                     DayTimeDuration::from_be_bytes(buffer),
                 ))
             }
-            _ => Err(Error::msg("the term buffer has an invalid type id")),
+            _ => Err(IoError::new(
+                ErrorKind::InvalidData,
+                "the term buffer has an invalid type id",
+            )),
         }
     }
 
-    fn read_spog_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_spog_quad(&mut self) -> IoResult<EncodedQuad> {
         let subject = self.read_term()?;
         let predicate = self.read_term()?;
         let object = self.read_term()?;
@@ -747,7 +750,7 @@ impl<R: Read> TermReader for R {
         })
     }
 
-    fn read_posg_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_posg_quad(&mut self) -> IoResult<EncodedQuad> {
         let predicate = self.read_term()?;
         let object = self.read_term()?;
         let subject = self.read_term()?;
@@ -760,7 +763,7 @@ impl<R: Read> TermReader for R {
         })
     }
 
-    fn read_ospg_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_ospg_quad(&mut self) -> IoResult<EncodedQuad> {
         let object = self.read_term()?;
         let subject = self.read_term()?;
         let predicate = self.read_term()?;
@@ -773,7 +776,7 @@ impl<R: Read> TermReader for R {
         })
     }
 
-    fn read_gspo_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_gspo_quad(&mut self) -> IoResult<EncodedQuad> {
         let graph_name = self.read_term()?;
         let subject = self.read_term()?;
         let predicate = self.read_term()?;
@@ -786,7 +789,7 @@ impl<R: Read> TermReader for R {
         })
     }
 
-    fn read_gpos_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_gpos_quad(&mut self) -> IoResult<EncodedQuad> {
         let graph_name = self.read_term()?;
         let predicate = self.read_term()?;
         let object = self.read_term()?;
@@ -799,7 +802,7 @@ impl<R: Read> TermReader for R {
         })
     }
 
-    fn read_gosp_quad(&mut self) -> Result<EncodedQuad> {
+    fn read_gosp_quad(&mut self) -> IoResult<EncodedQuad> {
         let graph_name = self.read_term()?;
         let object = self.read_term()?;
         let subject = self.read_term()?;
@@ -906,7 +909,7 @@ pub enum QuadEncoding {
 }
 
 impl QuadEncoding {
-    pub fn decode(self, buffer: &[u8]) -> Result<EncodedQuad> {
+    pub fn decode(self, buffer: &[u8]) -> IoResult<EncodedQuad> {
         let mut cursor = Cursor::new(&buffer);
         match self {
             QuadEncoding::SPOG => cursor.read_spog_quad(),
diff --git a/lib/src/store/rocksdb.rs b/lib/src/store/rocksdb.rs
index a580b908..488740c5 100644
--- a/lib/src/store/rocksdb.rs
+++ b/lib/src/store/rocksdb.rs
@@ -759,7 +759,7 @@ impl<'a> Iterator for DecodingIndexIterator<'a> {
     fn next(&mut self) -> Option<Result<EncodedQuad>> {
         if let Some(key) = self.iter.key() {
             if key.starts_with(&self.prefix) {
-                let result = self.encoding.decode(key);
+                let result = self.encoding.decode(key).map_err(crate::Error::from);
                 self.iter.next();
                 Some(result)
             } else {
diff --git a/lib/src/store/sled.rs b/lib/src/store/sled.rs
index d3a5bbb3..40f5f963 100644
--- a/lib/src/store/sled.rs
+++ b/lib/src/store/sled.rs
@@ -4,7 +4,7 @@ use crate::model::*;
 use crate::sparql::{GraphPattern, QueryOptions, QueryResult, SimplePreparedQuery};
 use crate::store::numeric_encoder::*;
 use crate::store::{load_dataset, load_graph, ReadableEncodedStore, WritableEncodedStore};
-use crate::{DatasetSyntax, GraphSyntax, Result};
+use crate::{DatasetSyntax, Error, GraphSyntax, Result};
 use sled::{Config, Iter, Tree};
 use std::io::BufRead;
 use std::path::Path;
@@ -556,7 +556,7 @@ impl Iterator for DecodingQuadIterator {
 
     fn next(&mut self) -> Option<Result<EncodedQuad>> {
         Some(match self.iter.next()? {
-            Ok((encoded, _)) => self.order.decode(&encoded),
+            Ok((encoded, _)) => self.order.decode(&encoded).map_err(Error::from),
             Err(error) => Err(error.into()),
         })
     }