diff --git a/bin/merge b/bin/merge
index 3dffa23a7950aadb93fdc7e00c948268c44663d5..d95cec685be87bda9a0de03dec7da0dfc8d6a798 100755
--- a/bin/merge
+++ b/bin/merge
@@ -45,24 +45,30 @@ function parseUrl() {
 }
 
 SOURCEBRANCH=$(git rev-parse --abbrev-ref HEAD)
-if [[ "$SOURCEBRANCH" == "main" ]]; then
-  echo "Main branch can not be merged."
-  exit 1
-elif [[ "$SOURCEBRANCH" == "develop" ]]; then
-  TARGETBRANCH=main
-else
-  TARGETBRANCH=develop
+if [[ "x$TARGETBRANCH" == "x" ]]; then
+  if [[ "$SOURCEBRANCH" == "main" ]]; then
+    echo "Main branch can not be merged."
+    exit 1
+  elif [[ "$SOURCEBRANCH" == "develop" ]]; then
+    TARGETBRANCH=main
+  else
+    TARGETBRANCH=develop
+  fi
+fi
+if [[ "$TARGETBRANCH" == "$SOURCEBRANCH" ]]; then
+  echo "Source and target branches must be different."
+  exit 2
 fi
 if [[ -n ${CI_SERVER_HOST} ]]; then
   GITLAB_URL=https://$CI_SERVER_HOST
 fi
 if [[ "x${GITLAB_URL}" == "x" ]]; then
   echo "Missing GITLAB_URL environment variable, should be set to e.g. https://gitlab.lakedrops.com"
-  exit 2
+  exit 3
 fi
 if [[ "x${GITLAB_PRIVATE_TOKEN}" == "x" ]]; then
   echo "Missing GITLAB_PRIVATE_TOKEN environment variable"
-  exit 3
+  exit 4
 fi
 parseUrl "$GITLAB_URL"
 host1=$host
@@ -70,7 +76,7 @@ parseUrl "$(git config remote.origin.url)"
 host2=$host
 if [[ "$host1" != "$host2" ]]; then
   echo "This repository doesn't match the provided GitLab instance"
-  exit 4
+  exit 5
 fi
 
 if [[ -n ${CI_PROJECT_ID} ]]; then
@@ -83,7 +89,7 @@ else
   PRJID=$(echo "$result"  | jq -r .[0]."id")
   if [[ $(isNumeric "$PRJID") -eq 1 ]]; then
     echo "Can not find project ID"
-    exit 5
+    exit 6
   fi
 fi
 
@@ -93,7 +99,7 @@ gitlab 201 POST projects/"$PRJID"/merge_requests --data "source_branch=$SOURCEBR
 MRID=$(echo "$result"  | jq -r ."iid")
 if [[ $(isNumeric "$MRID") -eq 1 ]]; then
   echo "Can not create merge request"
-  exit 6
+  exit 7
 fi
 echo "Created MR at $(echo "$result"  | jq -r ."web_url")"