diff --git a/include/cantera/kinetics/ReactionPath.h b/include/cantera/kinetics/ReactionPath.h
index 260f9add9..43e62a2f5 100644
--- a/include/cantera/kinetics/ReactionPath.h
+++ b/include/cantera/kinetics/ReactionPath.h
@@ -318,7 +318,12 @@ protected:
     std::vector<vector_int> m_groups;
     std::vector<Group> m_sgroup;
     std::vector<std::string> m_elementSymbols;
+
+    //! m_transfer[reaction][reactant number][product number] where "reactant
+    //! number" means the number of the reactant in the reaction equation, e.g.
+    //! for "A+B -> C+D", "B" is reactant number 1 and "C" is product number 0.
     std::map<size_t, std::map<size_t, std::map<size_t, Group> > > m_transfer;
+
     std::vector<bool> m_determinate;
     Array2D m_atoms;
     std::map<std::string, size_t> m_enamemap;
diff --git a/src/kinetics/ReactionPath.cpp b/src/kinetics/ReactionPath.cpp
index 61c3b0ccf..5a17ce79f 100644
--- a/src/kinetics/ReactionPath.cpp
+++ b/src/kinetics/ReactionPath.cpp
@@ -444,17 +444,17 @@ int ReactionPathBuilder::findGroups(ostream& logfile, Kinetics& s)
                     group_a0 = &r0;
                     group_b0 = &b0;
                     group_c0 = &p1;
-                    m_transfer[i][kr0][kp0] = r0;
-                    m_transfer[i][kr1][kp0] = b0;
-                    m_transfer[i][kr1][kp1] = p1;
+                    m_transfer[i][0][0] = r0;
+                    m_transfer[i][1][0] = b0;
+                    m_transfer[i][1][1] = p1;
                 } else {
                     group_a0 = &r1;
                     group_c0 = &p0;
                     b0 *= -1;
                     group_b0 = &b0;
-                    m_transfer[i][kr1][kp1] = r1;
-                    m_transfer[i][kr0][kp1] = b0;
-                    m_transfer[i][kr0][kp0] = p0;
+                    m_transfer[i][1][1] = r1;
+                    m_transfer[i][0][1] = b0;
+                    m_transfer[i][0][0] = p0;
                 }
                 logfile << "     ";
                 group_a0->fmt(logfile, m_elementSymbols);
@@ -479,9 +479,9 @@ int ReactionPathBuilder::findGroups(ostream& logfile, Kinetics& s)
                     group_b1 = &b1;
                     group_c1 = &p0;
                     if (!b0.valid()) {
-                        m_transfer[i][kr0][kp1] = r0;
-                        m_transfer[i][kr1][kp1] = b0;
-                        m_transfer[i][kr1][kp0] = p0;
+                        m_transfer[i][0][1] = r0;
+                        m_transfer[i][1][1] = b0;
+                        m_transfer[i][1][0] = p0;
                     }
                 } else {
                     group_a1 = &r1;
@@ -489,9 +489,9 @@ int ReactionPathBuilder::findGroups(ostream& logfile, Kinetics& s)
                     b1 *= -1;
                     group_b1 = &b1;
                     if (!b0.valid()) {
-                        m_transfer[i][kr1][kp0] = r1;
-                        m_transfer[i][kr0][kp0] = b0;
-                        m_transfer[i][kr0][kp1] = p1;
+                        m_transfer[i][1][0] = r1;
+                        m_transfer[i][0][0] = b0;
+                        m_transfer[i][0][1] = p1;
                     }
                 }
                 logfile << "     ";
@@ -768,10 +768,10 @@ int ReactionPathBuilder::build(Kinetics& s, const string& element,
                                 }
                                 f = 0.0;
                             } else {
-                                if (!g[kkr][kkp]) {
+                                if (!g[kr][kp]) {
                                     f = 0.0;
                                 } else {
-                                    f = g[kkr][kkp].nAtoms(m);
+                                    f = g[kr][kp].nAtoms(m);
                                 }
                             }
                         } else {