diff --git a/.Rbuildignore b/.Rbuildignore
index af21c6d..9c59904 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -1,2 +1,4 @@
 ^.*\.git$
-^README.md$
\ No newline at end of file
+^README.md$
+^.*\.Rproj$
+^\.Rproj\.user$
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..52c1c38
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+.Rproj.user
+.Rhistory
+.RData
+.Ruserdata
+*.Rproj
\ No newline at end of file
diff --git a/DESCRIPTION b/DESCRIPTION
index 8f8acdc..08d7d57 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: causaleffect
-Version: 1.3.12
-Date: 2020-12-18
+Version: 1.3.13
+Date: 2021-06-13
 Title: Deriving Expressions of Joint Interventional Distributions and Transport Formulas in Causal Models
 Authors@R: person(given = "Santtu",
     family = "Tikka",
diff --git a/NEWS b/NEWS
index b752a8c..dc32e75 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,6 @@
+Changes from version 1.3.12 to 1.3.13
+ * Fixed an incorrect graph definition in the IDC algorithm.
+
 Changes from version 1.3.11 to 1.3.12
  * The package no longer depends on the 'ggm' package.
  * The package no longer requires the 'XML' package, now suggests instead.
diff --git a/R/idc.R b/R/idc.R
index be10b00..8c20e86 100644
--- a/R/idc.R
+++ b/R/idc.R
@@ -5,13 +5,13 @@ idc <- function(y, x, z, P, G, G.obs, v, topo, tree, prune) {
   tree$branch <- list()
   offset <- (prune) * 2
   from <- NULL
-  G.xz <- unobserved.graph(G)
-  edges.to.x <- igraph::E(G.xz)[to(x)]
-  edges.from.z <- igraph::E(G.xz)[from(z)]
-  G.xz <- igraph::subgraph.edges(G.xz, igraph::E(G.xz)[setdiff(igraph::E(G.xz), union(edges.to.x, edges.from.z))], delete.vertices = FALSE)
+  G.u <- unobserved.graph(G)
+  edges.to.x <- igraph::E(G.u)[to(x)]
   nxt <- list()
   for (node in z) {
     cond <- setdiff(z, node)
+    edges.from.node <- igraph::E(G.u)[from(node)]
+    G.xz <- igraph::subgraph.edges(G.u, igraph::E(G.u)[setdiff(igraph::E(G.u), union(edges.to.x, edges.from.node))], delete.vertices = FALSE)
     if (wrap.dSep(G.xz, y, node, union(x, cond))) {
       tree$call$line <- 9 + offset
       tree$call$z.prime <- node
diff --git a/README.md b/README.md
index 70ccf0f..7e41aeb 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,9 @@ devtools::install_github("santikka/causaleffect")
 
 ## Recent changes (for all changes, see NEWS file).
 
+### Changes from version 1.3.12 to 1.3.13
+ * Fixed an incorrect graph definition in the IDC algorithm.
+
 ### Changes from version 1.3.11 to 1.3.12
  * The package no longer depends on the 'ggm' package.
  * The package no longer requires the 'XML' package, now suggests instead.
@@ -45,7 +48,3 @@ devtools::install_github("santikka/causaleffect")
 
 ### Changes from version 1.3.6 to 1.3.7
  * Fixed an issue with simplification introduced in version 1.3.6.
-
-### Changes from version 1.3.5 to 1.3.6
- * Fixed a bug regarding graphs where zero edges had the 'description' attribute.
- * Fixed a bug when attempting to simplify conditional causal effects.