diff --git a/tools/armature_manual.py b/tools/armature_manual.py
index da887fda..d035b93a 100644
--- a/tools/armature_manual.py
+++ b/tools/armature_manual.py
@@ -792,6 +792,9 @@ def execute(self, context):
 
         Common.switch('EDIT')
 
+        armature.data.use_mirror_x = False #<- fixes merge bones issues - @989onan
+        armature.pose.use_mirror_x = False #<- fixes merge bones issues - @989onan
+
         # Find which bones to work on and put their name and their parent in a list
         parenting_list = {}
         for bone in context.selected_editable_bones:
@@ -839,6 +842,9 @@ def execute(self, context):
 
         Common.switch('EDIT')
 
+        armature.data.use_mirror_x = False #<- fixes merge bones issues - @989onan
+        armature.pose.use_mirror_x = False #<- fixes merge bones issues - @989onan
+
         # Find which bones to work on and put their name and their parent in a list and parent the bones to the active one
         parenting_list = {}
         for bone in bpy.context.selected_editable_bones:
diff --git a/tools/common.py b/tools/common.py
index 484138b9..c990d559 100644
--- a/tools/common.py
+++ b/tools/common.py
@@ -272,6 +272,8 @@ def set_default_stage():
     armature = get_armature()
     if armature:
         set_active(armature)
+        armature.data.use_mirror_x = False #<- fixes merge bones issues - @989onan
+        armature.pose.use_mirror_x = False #<- fixes merge bones issues - @989onan
         if version_2_79_or_older():
             armature.layers[0] = True