diff --git a/src/ast/euf/euf_ac_plugin.cpp b/src/ast/euf/euf_ac_plugin.cpp
index 955f79c68..3f673598b 100644
--- a/src/ast/euf/euf_ac_plugin.cpp
+++ b/src/ast/euf/euf_ac_plugin.cpp
@@ -21,7 +21,7 @@ Completion modulo AC
 
 
   Notes: 
-  - Some equalities come from shared terms, so do not.
+  - Some equalities come from shared terms, some do not.
   
   - V2 can use multiplicities of elements to handle larger domains.
     - e.g. 3x + 100000y
@@ -77,7 +77,11 @@ namespace euf {
     {}
 
     void ac_plugin::register_node(enode* n) {
-        // no-op
+        if (is_op(n))
+            return;
+        for (auto arg : enode_args(n))
+            if (is_op(arg))
+                register_shared(arg); // TODO optimization to avoid registering shared terms twice
     }
 
     void ac_plugin::register_shared(enode* n) {
@@ -476,7 +480,7 @@ namespace euf {
         for (auto n : m)
             if (n->root->eqs.size() >= max_use)
                  max_n = n, max_use = n->root->eqs.size();
-        // found node that occurs in fewest rhs
+        // found node that occurs in most eqs
         VERIFY(max_n);
         m_eq_occurs.reset();
         for (auto n : m)
@@ -517,7 +521,7 @@ namespace euf {
         for (auto n : monomial(eq.l))
             if (n->root->eqs.size() < min_r)
                 min_n = n, min_r = n->root->eqs.size();
-        // found node that occurs in fewest rhs
+        // found node that occurs in fewest eqs
         VERIFY(min_n);
         return min_n->eqs;
     }
diff --git a/src/ast/euf/euf_ac_plugin.h b/src/ast/euf/euf_ac_plugin.h
index 4420469d5..88b4f6bb1 100644
--- a/src/ast/euf/euf_ac_plugin.h
+++ b/src/ast/euf/euf_ac_plugin.h
@@ -36,7 +36,7 @@ namespace euf {
 
     class ac_plugin : public plugin {
 
-        // enode structure for AC equivalenes
+        // enode structure for AC equivalences
         struct node {
             enode* n;        // associated enode
             node* root;      // path compressed root