diff --git a/scripts/update_api.py b/scripts/update_api.py
index 59811bf4c7b..00251765be9 100755
--- a/scripts/update_api.py
+++ b/scripts/update_api.py
@@ -1826,7 +1826,7 @@ def _to_pystr(s):
 
 push_eh_type  = ctypes.CFUNCTYPE(None, ctypes.c_void_p)
 pop_eh_type   = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_uint)
-fixed_eh_type = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p)
+fixed_eh_type = ctypes.CFUNCTYPE(None, ctypes.c_void_p, ctypes.c_void_p, ctypes.c_uint, ctypes.c_void_p)
 fresh_eh_type = ctypes.CFUNCTYPE(ctypes.c_void_p, ctypes.c_void_p)
 
 _lib.Z3_solver_propagate_init.restype = None
diff --git a/src/api/api_solver.cpp b/src/api/api_solver.cpp
index afcaa29db9a..726271131b4 100644
--- a/src/api/api_solver.cpp
+++ b/src/api/api_solver.cpp
@@ -899,7 +899,7 @@ extern "C" {
         init_solver(c, s);
         std::function<void(void*)> _push = push_eh;
         std::function<void(void*,unsigned)> _pop = pop_eh;
-        std::function<void(void*,unsigned,expr*)> _fixed = (void(*)(void*,unsigned,expr*))fixed_eh; 
+        std::function<void(void*,solver::propagate_callback*,unsigned,expr*)> _fixed = (void(*)(void*,solver::propagate_callback*,unsigned,expr*))fixed_eh; 
         std::function<void*(void*)> _fresh = fresh_eh;
         to_solver_ref(s)->user_propagate_init(user_context, _fixed, _push, _pop, _fresh);
         Z3_CATCH;
@@ -913,11 +913,11 @@ extern "C" {
         Z3_CATCH_RETURN(0);
     }
 
-    void Z3_API Z3_solver_propagate_consequence(Z3_context c, Z3_solver s, unsigned sz, unsigned const* ids, Z3_ast conseq) {
+    void Z3_API Z3_solver_propagate_consequence(Z3_context c, Z3_solver_callback s, unsigned sz, unsigned const* ids, Z3_ast conseq) {
         Z3_TRY;
         LOG_Z3_solver_propagate_consequence(c, s, sz, ids, conseq);
         RESET_ERROR_CODE();
-        to_solver_ref(s)->user_propagate_consequence(sz, ids, to_expr(conseq));
+        reinterpret_cast<solver::propagate_callback*>(s)->propagate(sz, ids, to_expr(conseq));
         Z3_CATCH;        
     }
 
diff --git a/src/api/python/z3/z3.py b/src/api/python/z3/z3.py
index c9760b05976..5e595b63bc0 100644
--- a/src/api/python/z3/z3.py
+++ b/src/api/python/z3/z3.py
@@ -10513,13 +10513,16 @@ def user_prop_push(ctx):
 def user_prop_pop(ctx, num_scopes):
     _user_propagate_bases[ctx].pop(num_scopes)
 
-def user_prop_fixed(ctx, id, value):
+def user_prop_fixed(ctx, cb, id, value):
     prop = _user_propagate_bases[ctx]
+    prop.cb = cb
     prop.fixed(id, _to_expr_ref(ctypes.c_void_p(value), prop.ctx))
+    prop.cb = None
 
 def user_prop_fresh(ctx):
     prop = _user_propagate_bases[ctx]
-    new_prop = prop.fresh()
+    new_prop = UsePropagateBase(None, prop.ctx)
+    _user_prop_bases[new_prop.id] = new_prop.fresh()
     return ctypes.c_void_p(new_prop.id)
     
 
@@ -10530,18 +10533,20 @@ def user_prop_fresh(ctx):
 
 class UserPropagateBase:
 
-    def __init__(self, s):
+    def __init__(self, s, ctx = None):
         self.id = len(_user_propagate_bases) + 3
         self.solver = s
-        self.ctx = s.ctx
+        self.ctx = s.ctx if s is not None else ctx
+        self.cb = None
         _user_propagate_bases[self.id] = self
-        Z3_solver_propagate_init(s.ctx.ref(),
-                                 s.solver,
-                                 ctypes.c_void_p(self.id),
-                                 _user_prop_push,
-                                 _user_prop_pop,
-                                 _user_prop_fixed,
-                                 _user_prop_fresh)
+        if s:
+            Z3_solver_propagate_init(s.ctx.ref(),
+                                     s.solver,
+                                     ctypes.c_void_p(self.id),
+                                     _user_prop_push,
+                                     _user_prop_pop,
+                                     _user_prop_fixed,
+                                     _user_prop_fresh)
         
     def push(self):
         raise Z3Exception("push has not been overwritten")
@@ -10551,19 +10556,23 @@ def pop(self, num_scopes):
 
     def fixed(self, id, e):
         raise Z3Exception("fixed has not been overwritten")
-
-    def fresh(self):
+    
+    def fresh(self, prop_base):
         raise Z3Exception("fresh has not been overwritten")
         
     def add(self, e):
+        assert self.solver
         return Z3_solver_propagate_register(self.ctx.ref(), self.solver.solver, e.ast)
 
+    #
+    # Propagation can only be invoked as during a fixed-callback.
+    # 
     def propagate(self, ids, e):
         sz = len(ids)
         _ids = (ctypes.c_uint * sz)()
         for i in range(sz):
             _ids[i] = ids[i]
-        Z3_solver_propagate_consequence(self.ctx.ref(), self.solver.solver, sz, _ids, e.ast)
+        Z3_solver_propagate_consequence(self.ctx.ref(), self.cb, sz, _ids, e.ast)
 
     def conflict(self, ids):
         self.propagate(ids, BoolVal(False, self.ctx))
diff --git a/src/api/python/z3/z3types.py b/src/api/python/z3/z3types.py
index d52a7914e2c..5c93b27a26e 100644
--- a/src/api/python/z3/z3types.py
+++ b/src/api/python/z3/z3types.py
@@ -82,6 +82,10 @@ class SolverObj(ctypes.c_void_p):
   def __init__(self, solver): self._as_parameter_ = solver
   def from_param(obj): return obj
 
+class SolverCallbackObj(ctypes.c_void_p):
+  def __init__(self, solver): self._as_parameter_ = solver
+  def from_param(obj): return obj
+
 class FixedpointObj(ctypes.c_void_p):
   def __init__(self, fixedpoint): self._as_parameter_ = fixedpoint
   def from_param(obj): return obj
diff --git a/src/api/z3_api.h b/src/api/z3_api.h
index 127bb90b1f3..921ce372d8d 100644
--- a/src/api/z3_api.h
+++ b/src/api/z3_api.h
@@ -25,6 +25,7 @@ DEFINE_TYPE(Z3_tactic);
 DEFINE_TYPE(Z3_probe);
 DEFINE_TYPE(Z3_stats);
 DEFINE_TYPE(Z3_solver);
+DEFINE_TYPE(Z3_solver_callback);
 DEFINE_TYPE(Z3_ast_vector);
 DEFINE_TYPE(Z3_ast_map);
 DEFINE_TYPE(Z3_apply_result);
@@ -1391,6 +1392,7 @@ typedef enum
   def_Type('CONSTRUCTOR',      'Z3_constructor',      'Constructor')
   def_Type('CONSTRUCTOR_LIST', 'Z3_constructor_list', 'ConstructorList')
   def_Type('SOLVER',           'Z3_solver',           'SolverObj')
+  def_Type('SOLVER_CALLBACK',  'Z3_solver_callback',  'SolverCallbackObj')
   def_Type('GOAL',             'Z3_goal',             'GoalObj')
   def_Type('TACTIC',           'Z3_tactic',           'TacticObj')
   def_Type('PARAMS',           'Z3_params',           'Params')
@@ -1418,7 +1420,7 @@ typedef void Z3_error_handler(Z3_context c, Z3_error_code e);
 */
 typedef void Z3_push_eh(void* ctx);
 typedef void Z3_pop_eh(void* ctx, unsigned num_scopes);
-typedef void Z3_fixed_eh(void* ctx, unsigned id, Z3_ast value);
+typedef void Z3_fixed_eh(void* ctx, Z3_solver_callback cb, unsigned id, Z3_ast value);
 typedef void* Z3_fresh_eh(void* ctx);
 
 /**
@@ -6553,10 +6555,10 @@ extern "C" {
        The callback adds a propagation consequence based on the fixed values of the
        \c ids. 
        
-       def_API('Z3_solver_propagate_consequence', VOID, (_in(CONTEXT), _in(SOLVER), _in(UINT), _in_array(2, UINT), _in(AST)))
+       def_API('Z3_solver_propagate_consequence', VOID, (_in(CONTEXT), _in(SOLVER_CALLBACK), _in(UINT), _in_array(2, UINT), _in(AST)))
     */
     
-    void Z3_API Z3_solver_propagate_consequence(Z3_context c, Z3_solver, unsigned sz, unsigned const* ids, Z3_ast conseq);
+    void Z3_API Z3_solver_propagate_consequence(Z3_context c, Z3_solver_callback, unsigned sz, unsigned const* ids, Z3_ast conseq);
 
     /**
        \brief Check whether the assertions in a given solver are consistent or not.
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index dca77ed29e1..77bab98d902 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -2951,7 +2951,7 @@ namespace smt {
 
     void context::user_propagate_init(
         void* ctx, 
-        std::function<void(void*, unsigned, expr*)>& fixed_eh,
+        std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
         std::function<void(void*)>&                  push_eh,
         std::function<void(void*, unsigned)>&        pop_eh,
         std::function<void*(void*)>&                 fresh_eh) {
diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h
index ebef0e80711..4bacac97bf1 100644
--- a/src/smt/smt_context.h
+++ b/src/smt/smt_context.h
@@ -1689,7 +1689,7 @@ namespace smt {
          */
         void user_propagate_init(
             void* ctx, 
-            std::function<void(void*, unsigned, expr*)>& fixed_eh,
+            std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
             std::function<void(void*)>&                  push_eh,
             std::function<void(void*, unsigned)>&        pop_eh,
             std::function<void*(void*)>&                 fresh_eh);
@@ -1700,13 +1700,6 @@ namespace smt {
             return m_user_propagator->add_expr(e);
         }
         
-        void user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq) {
-            if (!m_user_propagator) 
-                throw default_exception("user propagator must be initialized");
-            m_user_propagator->add_propagation(sz, ids, conseq);
-        }
-
-
         bool watches_fixed(enode* n) const;
 
         void assign_fixed(enode* n, expr* val, unsigned sz, literal const* explain);
diff --git a/src/smt/smt_kernel.cpp b/src/smt/smt_kernel.cpp
index ca8ea5a376b..567f0eef593 100644
--- a/src/smt/smt_kernel.cpp
+++ b/src/smt/smt_kernel.cpp
@@ -235,7 +235,7 @@ namespace smt {
 
         void user_propagate_init(
             void* ctx, 
-            std::function<void(void*, unsigned, expr*)>& fixed_eh,
+            std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
             std::function<void(void*)>&                  push_eh,
             std::function<void(void*, unsigned)>&        pop_eh,
             std::function<void*(void*)>&                 fresh_eh) {
@@ -246,9 +246,6 @@ namespace smt {
             return m_kernel.user_propagate_register(e);
         }
         
-        void user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq) {
-            m_kernel.user_propagate_consequence(sz, ids, conseq);
-        }
     };
 
     kernel::kernel(ast_manager & m, smt_params & fp, params_ref const & p) {
@@ -463,7 +460,7 @@ namespace smt {
 
     void kernel::user_propagate_init(
         void* ctx, 
-        std::function<void(void*, unsigned, expr*)>& fixed_eh,
+        std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
         std::function<void(void*)>&                  push_eh,
         std::function<void(void*, unsigned)>&        pop_eh,
         std::function<void*(void*)>&                 fresh_eh) {
@@ -472,12 +469,6 @@ namespace smt {
 
     unsigned kernel::user_propagate_register(expr* e) {
         return m_imp->user_propagate_register(e);
-    }
-        
-    void kernel::user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq) {
-        m_imp->user_propagate_consequence(sz, ids, conseq);
-    }
-
-
+    }        
 
 };
diff --git a/src/smt/smt_kernel.h b/src/smt/smt_kernel.h
index 126e4c20f33..3eac0bc188f 100644
--- a/src/smt/smt_kernel.h
+++ b/src/smt/smt_kernel.h
@@ -26,11 +26,12 @@ Revision History:
 --*/
 #pragma once
 
-#include "ast/ast.h"
 #include "util/params.h"
-#include "model/model.h"
 #include "util/lbool.h"
 #include "util/statistics.h"
+#include "ast/ast.h"
+#include "model/model.h"
+#include "solver/solver.h"
 #include "smt/smt_failure.h"
 
 struct smt_params;
@@ -289,7 +290,7 @@ namespace smt {
         */
         void user_propagate_init(
             void* ctx, 
-            std::function<void(void*, unsigned, expr*)>& fixed_eh,
+            std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
             std::function<void(void*)>&                  push_eh,
             std::function<void(void*, unsigned)>&        pop_eh,
             std::function<void*(void*)>&                 fresh_eh);
@@ -298,13 +299,6 @@ namespace smt {
            \brief register an expression to be tracked fro user propagation.
         */
         unsigned user_propagate_register(expr* e);
-
-
-        /**
-           \brief accept a user-propagation callback (issued during fixed_he).
-        */
-        
-        void user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq);
         
 
         /**
diff --git a/src/smt/smt_solver.cpp b/src/smt/smt_solver.cpp
index 382bc9d3e4e..eddc0e0d35b 100644
--- a/src/smt/smt_solver.cpp
+++ b/src/smt/smt_solver.cpp
@@ -210,7 +210,7 @@ namespace {
 
         void user_propagate_init(
             void* ctx, 
-            std::function<void(void*, unsigned, expr*)>& fixed_eh,
+            std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
             std::function<void(void*)>&                  push_eh,
             std::function<void(void*, unsigned)>&        pop_eh,
             std::function<void*(void*)>&                 fresh_eh) override {
@@ -221,10 +221,6 @@ namespace {
             return m_context.user_propagate_register(e);
         }
 
-        void user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq) override {
-            m_context.user_propagate_consequence(sz, ids, conseq);
-        }        
-
         struct scoped_minimize_core {
             smt_solver& s;
             expr_ref_vector m_assumptions;
diff --git a/src/smt/user_propagator.cpp b/src/smt/user_propagator.cpp
index 114d3fd7e75..5c401fffffd 100644
--- a/src/smt/user_propagator.cpp
+++ b/src/smt/user_propagator.cpp
@@ -49,7 +49,7 @@ unsigned user_propagator::add_expr(expr* e) {
     return v;
 }
 
-void user_propagator::add_propagation(unsigned sz, unsigned const* ids, expr* conseq) {
+void user_propagator::propagate(unsigned sz, unsigned const* ids, expr* conseq) {
     m_prop.push_back(prop_info(sz, ids, expr_ref(conseq, m)));
 }
 
@@ -63,7 +63,7 @@ theory * user_propagator::mk_fresh(context * new_ctx) {
 void user_propagator::new_fixed_eh(theory_var v, expr* value, unsigned num_lits, literal const* jlits) {
     force_push();
     m_id2justification.setx(v, literal_vector(num_lits, jlits), literal_vector());
-    m_fixed_eh(m_user_context, v, value);
+    m_fixed_eh(m_user_context, this, v, value);
 }
 
 void user_propagator::push_scope_eh() {
diff --git a/src/smt/user_propagator.h b/src/smt/user_propagator.h
index 208e9447326..db845086566 100644
--- a/src/smt/user_propagator.h
+++ b/src/smt/user_propagator.h
@@ -25,11 +25,12 @@ Module Name:
 #pragma once
 
 #include "smt/smt_theory.h"
+#include "solver/solver.h"
 
 namespace smt {
-    class user_propagator : public theory {
+    class user_propagator : public theory, public solver::propagate_callback {
         void* m_user_context;
-        std::function<void(void*, unsigned, expr*)> m_fixed_eh;
+        std::function<void(void*, solver::propagate_callback*, unsigned, expr*)> m_fixed_eh;
         std::function<void(void*)>                  m_push_eh;
         std::function<void(void*, unsigned)>        m_pop_eh;
         std::function<void*(void*)>                 m_fresh_eh;
@@ -60,7 +61,7 @@ namespace smt {
          */
         void add(
             void* ctx, 
-            std::function<void(void*, unsigned, expr*)>& fixed_eh,
+            std::function<void(void*, solver::propagate_callback*, unsigned, expr*)>& fixed_eh,
             std::function<void(void*)>&                  push_eh,
             std::function<void(void*, unsigned)>&        pop_eh,
             std::function<void*(void*)>&                 fresh_eh) {
@@ -73,7 +74,7 @@ namespace smt {
 
         unsigned add_expr(expr* e);
 
-        void add_propagation(unsigned sz, unsigned const* ids, expr* conseq);
+        void propagate(unsigned sz, unsigned const* ids, expr* conseq) override;
 
         void new_fixed_eh(theory_var v, expr* value, unsigned num_lits, literal const* jlits);
 
diff --git a/src/solver/solver.h b/src/solver/solver.h
index 14379e2f6e3..f5452029d5f 100644
--- a/src/solver/solver.h
+++ b/src/solver/solver.h
@@ -238,9 +238,14 @@ class solver : public check_sat_result {
 
     virtual expr_ref get_implied_upper_bound(expr* e) = 0;
 
+    class propagate_callback {
+    public:
+        virtual void propagate(unsigned sz, unsigned const* ids, expr* conseq) = 0;
+    };
+
     virtual void user_propagate_init(
         void* ctx, 
-        std::function<void(void*, unsigned, expr*)>& fixed_eh,
+        std::function<void(void*, propagate_callback*, unsigned, expr*)>& fixed_eh,
         std::function<void(void*)>&                  push_eh,
         std::function<void(void*, unsigned)>&        pop_eh,
         std::function<void*(void*)>&                 fresh_eh) {
@@ -249,8 +254,6 @@ class solver : public check_sat_result {
 
     virtual unsigned user_propagate_register(expr* e) { return 0; }
 
-    virtual void user_propagate_consequence(unsigned sz, unsigned const* ids, expr* conseq) {}
-
 
     /**
        \brief Display the content of this solver.