diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index d5bfa3fa966c7c2cfff3fade38e1db776244451d..ffa5321c61faf2a9713c65edf6cb4b4553b1eb26 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -6,7 +6,7 @@ FROM mcr.microsoft.com/vscode/devcontainers/cpp:0-${VARIANT}
 
 # [Optional] Uncomment this section to install additional packages.
 RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
-    && apt-get -y install --no-install-recommends wget cmake bison flex \
+    && apt-get -y install --no-install-recommends wget cmake bison flex graphviz \
     openmpi-bin libopenmpi-dev && \
     wget http://www.lrde.epita.fr/dload/spot/spot-2.10.4.tar.gz && \
     tar xzf spot-2.10.4.tar.gz && cd spot-2.10.4 && \
diff --git a/src/main.cpp b/src/main.cpp
index 6847eda2a6cd12a948385803a867e4c7a4137b80..b94d3bd64675c00b8b55714a1534e8a1638e2e08 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -590,7 +590,7 @@ int main(int argc, char **argv)
                         spot::twa::prop_set::all(), true);
                     if (dot_sog)
                     {
-                        saveGraph(af, "SOG.dot", "ka");
+                        saveGraph(k, "SOG.dot", "ka");
                     }
                     cout << endl;