diff --git a/bin/llvm-kompile-testing b/bin/llvm-kompile-testing
index f3430803b..e92df5576 100755
--- a/bin/llvm-kompile-testing
+++ b/bin/llvm-kompile-testing
@@ -11,7 +11,17 @@ trap 'rm -rf "$dt_dir"' INT TERM EXIT
 definition=$(realpath "$1")
 mode="$2"
 shift; shift
-( cd "@PROJECT_SOURCE_DIR@"/matching && mvn exec:java -Dexec.args="$definition qbaL $dt_dir 1" -q )
+
+matching_dir="@PROJECT_SOURCE_DIR@/matching"
+installed_jar="$matching_dir/target/llvm-backend-matching-1.0-SNAPSHOT-jar-with-dependencies.jar"
+
+if [ ! -f "$installed_jar" ]; then
+  echo "Pattern matching compiler isn't installed!"
+  echo "  looking for a jar file at $installed_jar"
+  exit 1
+fi
+
+java -jar "$installed_jar" "$definition" qbaL "$dt_dir" 1
 
 llvm_kompile_flags=()
 clang_flags=()
diff --git a/nix/overlay.nix b/nix/overlay.nix
index 0fbd819ae..a6b3d76de 100644
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -45,9 +45,11 @@ let
     mkdir -p "$out/bin"
     cp ${llvm-backend.src}/bin/llvm-kompile-testing "$out/bin"
     sed -i "$out/bin/llvm-kompile-testing" \
-        -e '/@PROJECT_SOURCE_DIR@/ c ${java} -jar ${jar} $definition qbaL $dt_dir 1'
+        -e 's!installed_jar=.*!installed_jar="${jar}"!g'
     substituteInPlace $out/bin/llvm-kompile-testing \
-      --replace 'llvm-kompile' '${llvm-backend}/bin/llvm-kompile'
+      --replace 'llvm-kompile' '${llvm-backend}/bin/llvm-kompile' \
+      --replace 'java -jar "$installed_jar" "$definition" qbaL "$dt_dir" 1' \
+                '${java} -jar "$installed_jar" "$definition" qbaL "$dt_dir" 1'
     chmod +x "$out/bin/llvm-kompile-testing"
     patchShebangs "$out/bin/llvm-kompile-testing"
   '';