diff --git a/src/force.cpp b/src/force.cpp
index 14d48d1a73..67187f8dd6 100644
--- a/src/force.cpp
+++ b/src/force.cpp
@@ -336,6 +336,8 @@ void Force::create_bond(const std::string &style, int trysuffix)
 {
   delete[] bond_style;
   if (bond) delete bond;
+  bond_style = nullptr;
+  bond = nullptr;
 
   int sflag;
   bond = new_bond(style, trysuffix, sflag);
@@ -404,6 +406,8 @@ void Force::create_angle(const std::string &style, int trysuffix)
 {
   delete[] angle_style;
   if (angle) delete angle;
+  angle_style = nullptr;
+  angle = nullptr;
 
   int sflag;
   angle = new_angle(style, trysuffix, sflag);
@@ -472,6 +476,8 @@ void Force::create_dihedral(const std::string &style, int trysuffix)
 {
   delete[] dihedral_style;
   if (dihedral) delete dihedral;
+  dihedral_style = nullptr;
+  dihedral = nullptr;
 
   int sflag;
   dihedral = new_dihedral(style, trysuffix, sflag);
@@ -540,6 +546,8 @@ void Force::create_improper(const std::string &style, int trysuffix)
 {
   delete[] improper_style;
   if (improper) delete improper;
+  improper_style = nullptr;
+  improper = nullptr;
 
   int sflag;
   improper = new_improper(style, trysuffix, sflag);
@@ -608,6 +616,8 @@ void Force::create_kspace(const std::string &style, int trysuffix)
 {
   delete[] kspace_style;
   if (kspace) delete kspace;
+  kspace_style = nullptr;
+  kspace = nullptr;
 
   int sflag;
   kspace = new_kspace(style, trysuffix, sflag);
diff --git a/src/update.cpp b/src/update.cpp
index 04d3f7e1e6..1704e7c439 100644
--- a/src/update.cpp
+++ b/src/update.cpp
@@ -332,6 +332,8 @@ void Update::create_integrate(int narg, char **arg, int trysuffix)
 
   delete[] integrate_style;
   delete integrate;
+  integrate_style = nullptr;
+  integrate = nullptr;
 
   int sflag;
 
@@ -400,6 +402,8 @@ void Update::create_minimize(int narg, char **arg, int trysuffix)
 
   delete[] minimize_style;
   delete minimize;
+  minimize_style = nullptr;
+  minimize = nullptr;
 
   // temporarily assign the style name without suffix (for error messages during creation)
   minimize_style = arg[0];