diff --git a/CHANGES.md b/CHANGES.md
index d57c65b9..c0ce4552 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -17,10 +17,12 @@
       * added option to set false assumptions
       * type parsing and defaults for user input in `_context_value`
       * model selection now accepts show statements for filtering
+      * added operation to set a constant
     * Domain constructors
       * added optimization information into domain state
       * added information about externals
       * added automatic check to skip constructors based on `ui files`
+      * added information about the constants
     * Examples
       * New example with incremental solving
       * New examples with optimization and false assumptions
diff --git a/clinguin/server/application/backends/clingo_backend.py b/clinguin/server/application/backends/clingo_backend.py
index 43e258a8..25595a6c 100644
--- a/clinguin/server/application/backends/clingo_backend.py
+++ b/clinguin/server/application/backends/clingo_backend.py
@@ -214,6 +214,7 @@ def _init_ds_constructors(self):
         self._domain_state_constructors = []
         self._backup_ds_cache = {}
         self._add_domain_state_constructor("_ds_context")
+        self._add_domain_state_constructor("_ds_constants")
         self._add_domain_state_constructor("_ds_browsing")
         self._add_domain_state_constructor("_ds_cautious_optimal")
         self._add_domain_state_constructor("_ds_brave_optimal")
@@ -1062,7 +1063,7 @@ def clear_assumptions(self):
         self._outdate()
         self._assumptions = set()
 
-    def add_assumption(self, atom, value):
+    def add_assumption(self, atom, value="true"):
         """
         Adds an atom `a` as an assumption.
         If the value is True, the atom is assumed to be true.
diff --git a/clinguin/server/application/backends/explanation_backend.py b/clinguin/server/application/backends/explanation_backend.py
index d1e5b432..3c008f36 100644
--- a/clinguin/server/application/backends/explanation_backend.py
+++ b/clinguin/server/application/backends/explanation_backend.py
@@ -46,18 +46,6 @@ def _assumption_list(self):
     # Initialization
     # ---------------------------------------------
 
-    @extends(ClingoBackend)
-    def _init_interactive(self):
-        """
-        Adds the MUS property
-
-        Attributes:
-            _mus (str): The list of assumptions in the MUS property
-        """
-        super()._init_interactive()
-        # pylint: disable= attribute-defined-outside-init
-        self._mus = None
-
     @extends(ClingoBackend)
     def _init_command_line(self):
         """
@@ -72,7 +60,8 @@ def _init_command_line(self):
         self._assumption_sig = []
         for a in self._args.assumption_signature or []:
             try:
-                self._assumption_sig.append((a.split(",")[0], int(a.split(",")[1])))
+                name, arity = a.split(",")
+                self._assumption_sig.append((name, int(arity)))
             except Exception as ex:
                 raise ValueError(
                     "Argument assumption_signature must have format name,arity"