diff --git a/src/USER-REAXC/pair_reax_c.cpp b/src/USER-REAXC/pair_reax_c.cpp
index a83ee1b5cc..f67100d789 100644
--- a/src/USER-REAXC/pair_reax_c.cpp
+++ b/src/USER-REAXC/pair_reax_c.cpp
@@ -763,7 +763,7 @@ void PairReaxC::read_reax_forces()
 
 /* ---------------------------------------------------------------------- */
 
-void *PairReaxC::extract(char *str, int &dim)
+void *PairReaxC::extract(const char *str, int &dim)
 {
   dim = 1;
   if (strcmp(str,"chi") == 0 && chi) {
diff --git a/src/USER-REAXC/pair_reax_c.h b/src/USER-REAXC/pair_reax_c.h
index 8fd14f6053..cfd9e35937 100644
--- a/src/USER-REAXC/pair_reax_c.h
+++ b/src/USER-REAXC/pair_reax_c.h
@@ -44,7 +44,7 @@ class PairReaxC : public Pair {
   void coeff(int, char **);
   void init_style();
   double init_one(int, int);
-  void *extract(char *, int &);
+  void *extract(const char *, int &);
   int fixbond_flag, fixspecies_flag;
 
   control_params *control;