diff --git a/src/CLASS2/bond_class2.cpp b/src/CLASS2/bond_class2.cpp
index 097c8fe387..7feec1a4b3 100644
--- a/src/CLASS2/bond_class2.cpp
+++ b/src/CLASS2/bond_class2.cpp
@@ -224,7 +224,7 @@ double BondClass2::single(int type, double rsq, int /*i*/, int /*j*/, double &ff
 
 /* ---------------------------------------------------------------------- */
 
-void *BondClass2::extract( char *str, int &dim )
+void *BondClass2::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"r0")==0) return (void*) r0;
diff --git a/src/CLASS2/bond_class2.h b/src/CLASS2/bond_class2.h
index fb7eb884df..f83fecfce0 100644
--- a/src/CLASS2/bond_class2.h
+++ b/src/CLASS2/bond_class2.h
@@ -35,7 +35,7 @@ class BondClass2 : public Bond {
   virtual void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double *r0,*k2,*k3,*k4;
diff --git a/src/MOLECULE/bond_fene.cpp b/src/MOLECULE/bond_fene.cpp
index e3c47b6241..91c0877478 100644
--- a/src/MOLECULE/bond_fene.cpp
+++ b/src/MOLECULE/bond_fene.cpp
@@ -276,7 +276,7 @@ double BondFENE::single(int type, double rsq, int /*i*/, int /*j*/,
 
 /* ---------------------------------------------------------------------- */
 
-void *BondFENE::extract( char *str, int &dim )
+void *BondFENE::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"kappa")==0) return (void*) k;
diff --git a/src/MOLECULE/bond_fene.h b/src/MOLECULE/bond_fene.h
index 77c7db1200..78ce169870 100644
--- a/src/MOLECULE/bond_fene.h
+++ b/src/MOLECULE/bond_fene.h
@@ -36,7 +36,7 @@ class BondFENE : public Bond {
   void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double TWO_1_3;
diff --git a/src/MOLECULE/bond_gromos.cpp b/src/MOLECULE/bond_gromos.cpp
index 6732cc4457..27447d7298 100644
--- a/src/MOLECULE/bond_gromos.cpp
+++ b/src/MOLECULE/bond_gromos.cpp
@@ -189,7 +189,7 @@ void BondGromos::write_data(FILE *fp)
 /* ---------------------------------------------------------------------- */
 
 double BondGromos::single(int type, double rsq, int /*i*/, int /*j*/,
-                        double &fforce)
+                          double &fforce)
 {
   double dr = rsq - r0[type]*r0[type];
   fforce = -4.0*k[type] * dr;
@@ -199,7 +199,7 @@ double BondGromos::single(int type, double rsq, int /*i*/, int /*j*/,
 /* ----------------------------------------------------------------------
     Return ptr to internal members upon request.
 ------------------------------------------------------------------------ */
-void *BondGromos::extract( char *str, int &dim )
+void *BondGromos::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"kappa")==0) return (void*) k;
diff --git a/src/MOLECULE/bond_gromos.h b/src/MOLECULE/bond_gromos.h
index 966b914437..95ecf8db10 100644
--- a/src/MOLECULE/bond_gromos.h
+++ b/src/MOLECULE/bond_gromos.h
@@ -35,7 +35,7 @@ class BondGromos : public Bond {
   void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double *k,*r0;
diff --git a/src/MOLECULE/bond_harmonic.cpp b/src/MOLECULE/bond_harmonic.cpp
index 569c92f99d..5ea60cda46 100644
--- a/src/MOLECULE/bond_harmonic.cpp
+++ b/src/MOLECULE/bond_harmonic.cpp
@@ -190,7 +190,7 @@ void BondHarmonic::write_data(FILE *fp)
 /* ---------------------------------------------------------------------- */
 
 double BondHarmonic::single(int type, double rsq, int /*i*/, int /*j*/,
-                        double &fforce)
+                            double &fforce)
 {
   double r = sqrt(rsq);
   double dr = r - r0[type];
@@ -203,7 +203,7 @@ double BondHarmonic::single(int type, double rsq, int /*i*/, int /*j*/,
 /* ----------------------------------------------------------------------
     Return ptr to internal members upon request.
 ------------------------------------------------------------------------ */
-void *BondHarmonic::extract( char *str, int &dim )
+void *BondHarmonic::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"kappa")==0) return (void*) k;
diff --git a/src/MOLECULE/bond_harmonic.h b/src/MOLECULE/bond_harmonic.h
index 576e63629b..39b4f68af5 100644
--- a/src/MOLECULE/bond_harmonic.h
+++ b/src/MOLECULE/bond_harmonic.h
@@ -35,7 +35,7 @@ class BondHarmonic : public Bond {
   virtual void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double *k,*r0;
diff --git a/src/MOLECULE/bond_morse.cpp b/src/MOLECULE/bond_morse.cpp
index 0a92229879..c644d2be1c 100644
--- a/src/MOLECULE/bond_morse.cpp
+++ b/src/MOLECULE/bond_morse.cpp
@@ -209,7 +209,7 @@ double BondMorse::single(int type, double rsq, int /*i*/, int /*j*/,
 
 /* ---------------------------------------------------------------------- */
 
-void *BondMorse::extract(char *str, int &dim )
+void *BondMorse::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"r0")==0) return (void*) r0;
diff --git a/src/MOLECULE/bond_morse.h b/src/MOLECULE/bond_morse.h
index cbab0aed1d..6d7ec8f8aa 100644
--- a/src/MOLECULE/bond_morse.h
+++ b/src/MOLECULE/bond_morse.h
@@ -35,7 +35,7 @@ class BondMorse : public Bond {
   void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double *d0,*alpha,*r0;
diff --git a/src/MOLECULE/bond_nonlinear.cpp b/src/MOLECULE/bond_nonlinear.cpp
index 8f0616e03e..1451fa29c2 100644
--- a/src/MOLECULE/bond_nonlinear.cpp
+++ b/src/MOLECULE/bond_nonlinear.cpp
@@ -206,7 +206,7 @@ double BondNonlinear::single(int type, double rsq, int /*i*/, int /*j*/,
 
 /* ---------------------------------------------------------------------- */
 
-void *BondNonlinear::extract( char *str, int &dim )
+void *BondNonlinear::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"epsilon")==0) return (void*) epsilon;
diff --git a/src/MOLECULE/bond_nonlinear.h b/src/MOLECULE/bond_nonlinear.h
index 76dffdba31..29191698d3 100644
--- a/src/MOLECULE/bond_nonlinear.h
+++ b/src/MOLECULE/bond_nonlinear.h
@@ -35,7 +35,7 @@ class BondNonlinear : public Bond {
   void read_restart(FILE *);
   void write_data(FILE *);
   double single(int, double, int, int, double &);
-  virtual void *extract(char *, int &);
+  virtual void *extract(const char *, int &);
 
  protected:
   double *epsilon,*r0,*lamda;
diff --git a/src/bond.h b/src/bond.h
index b558a2a35e..8d7585b388 100644
--- a/src/bond.h
+++ b/src/bond.h
@@ -52,7 +52,7 @@ class Bond : protected Pointers {
   virtual void write_data(FILE *) {}
   virtual double single(int, double, int, int, double &) = 0;
   virtual double memory_usage();
-  virtual void *extract(char *, int &) {return NULL;}
+  virtual void *extract(const char *, int &) {return NULL;}
   virtual void reinit();
 
   void write_file(int, char**);