diff --git a/src/PYTHON/fix_python_invoke.cpp b/src/PYTHON/fix_python_invoke.cpp
index b47a94c6c7..6f27831438 100644
--- a/src/PYTHON/fix_python_invoke.cpp
+++ b/src/PYTHON/fix_python_invoke.cpp
@@ -72,7 +72,11 @@ FixPythonInvoke::FixPythonInvoke(LAMMPS *lmp, int narg, char **arg) :
 
   lmpPtr = PY_VOID_POINTER(lmp);
 
-  modify->addstep_compute_all(nextvalid());
+  // nvalid = next step on which end_of_step or post_force does something
+  // add nextvalid() to all computes that store invocation times
+  // since we don't know a priori which are invoked by python code
+  nvalid = nextvalid();
+  modify->addstep_compute_all(nvalid);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -92,8 +96,21 @@ int FixPythonInvoke::setmask()
 
 /* ---------------------------------------------------------------------- */
 
+void FixPythonInvoke::init()
+{
+  // need to reset nvalid if nvalid < ntimestep b/c minimize was performed
+
+  if (nvalid < update->ntimestep) {
+    nvalid = nextvalid();
+    modify->addstep_compute_all(nvalid);
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
 void FixPythonInvoke::end_of_step()
 {
+  // python code may invoke computes so wrap with clear/add
   modify->clearstep_compute();
 
   PyUtils::GIL lock;
@@ -107,7 +124,8 @@ void FixPythonInvoke::end_of_step()
 
   Py_CLEAR(result);
 
-  modify->addstep_compute(nextvalid());
+  nvalid = nextvalid();
+  modify->addstep_compute(nvalid);
 }
 
 /* ---------------------------------------------------------------------- */
@@ -123,6 +141,7 @@ void FixPythonInvoke::post_force(int vflag)
 {
   if (update->ntimestep % nevery != 0) return;
 
+  // python code may invoke computes so wrap with clear/add
   modify->clearstep_compute();
 
   PyUtils::GIL lock;
@@ -137,7 +156,8 @@ void FixPythonInvoke::post_force(int vflag)
 
   Py_CLEAR(result);
 
-  modify->addstep_compute(nextvalid());
+  nvalid = nextvalid();
+  modify->addstep_compute(nvalid);
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/PYTHON/fix_python_invoke.h b/src/PYTHON/fix_python_invoke.h
index 3d2324a939..fdb931b69c 100644
--- a/src/PYTHON/fix_python_invoke.h
+++ b/src/PYTHON/fix_python_invoke.h
@@ -31,6 +31,7 @@ class FixPythonInvoke : public Fix {
   ~FixPythonInvoke() override;
   int setmask() override;
   void setup(int) override;
+  void init() override;
   void end_of_step() override;
   void post_force(int) override;
 
@@ -39,6 +40,7 @@ class FixPythonInvoke : public Fix {
   void *pFunc;
   int selected_callback;
   bigint nextvalid();
+  bigint nvalid;
 };
 
 }    // namespace LAMMPS_NS