diff --git a/src/compute.h b/src/compute.h
index 7f12cd97e20d1c25b5d6b4e9eddffd81cd2657a5..279f71829bd8d86b1ea36f5b6a89b69fd64c2154 100644
--- a/src/compute.h
+++ b/src/compute.h
@@ -152,7 +152,7 @@ class Compute : protected Pointers {
   double **vbiasall;           // stored velocity bias for all atoms
   int maxbias;                 // size of vbiasall array
 
-  inline int sbmask(int j) {
+  inline int sbmask(int j) const {
     return j >> SBBITS & 3;
   }
 
diff --git a/src/create_bonds.h b/src/create_bonds.h
index 2936506b3fd0afac9b08557d8e40cf382addc325..24b1596e37ad68b8d6d5115a2a5e124a922e5a7f 100644
--- a/src/create_bonds.h
+++ b/src/create_bonds.h
@@ -30,7 +30,7 @@ class CreateBonds : protected Pointers {
   void command(int, char **);
 
  private:
-  inline int sbmask(int j) {
+  inline int sbmask(int j) const {
     return j >> SBBITS & 3;
   }
 };
diff --git a/src/delete_atoms.h b/src/delete_atoms.h
index 62ba47d715d47efab94161362d21c5dcfa542847..72cf44285f813c626980f8a16b3ce8fb31644e9d 100644
--- a/src/delete_atoms.h
+++ b/src/delete_atoms.h
@@ -45,7 +45,7 @@ class DeleteAtoms : protected Pointers {
   void recount_topology();
   void options(int, char **);
 
-  inline int sbmask(int j) {
+  inline int sbmask(int j) const {
     return j >> SBBITS & 3;
   }
 
diff --git a/src/pair.h b/src/pair.h
index dd859e5f2a07ca2b99ba288302a03b2f17d1cbbe..b57004d965c535b7583597b04b01fd6c22e7a61d 100644
--- a/src/pair.h
+++ b/src/pair.h
@@ -245,7 +245,7 @@ class Pair : protected Pointers {
     ubuf(int arg) : i(arg) {}
   };
 
-  inline int sbmask(int j) {
+  inline int sbmask(int j) const {
     return j >> SBBITS & 3;
   }
 };