diff --git a/infer/src/absint/NodePrinter.ml b/infer/src/absint/NodePrinter.ml
index 3855ae962..89d6dff66 100644
--- a/infer/src/absint/NodePrinter.ml
+++ b/infer/src/absint/NodePrinter.ml
@@ -18,8 +18,8 @@ let new_session node =
       0
   | Some summary ->
       Summary.Stats.add_visited summary.stats node_id ;
-      incr summary.Summary.sessions ;
-      !(summary.Summary.sessions)
+      summary.Summary.sessions <- summary.Summary.sessions + 1 ;
+      summary.Summary.sessions
 
 
 let kind_to_string = function
diff --git a/infer/src/backend/Summary.ml b/infer/src/backend/Summary.ml
index bed8b68a9..f1470679d 100644
--- a/infer/src/backend/Summary.ml
+++ b/infer/src/backend/Summary.ml
@@ -66,7 +66,7 @@ include struct
 
   type t =
     { payloads: Payloads.t
-    ; sessions: int ref
+    ; mutable sessions: int
     ; stats: Stats.t
     ; status: Status.t
     ; proc_desc: Procdesc.t
@@ -256,7 +256,7 @@ module OnDisk = struct
 
   let reset proc_desc =
     let summary =
-      { sessions= ref 0
+      { sessions= 0
       ; payloads= Payloads.empty
       ; stats= Stats.empty
       ; status= Status.Pending
diff --git a/infer/src/backend/Summary.mli b/infer/src/backend/Summary.mli
index e33e3c3b0..64407a521 100644
--- a/infer/src/backend/Summary.mli
+++ b/infer/src/backend/Summary.mli
@@ -42,7 +42,7 @@ end
 (** summary of a procedure name *)
 type t =
   { payloads: Payloads.t
-  ; sessions: int ref  (** Session number: how many nodes went through symbolic execution *)
+  ; mutable sessions: int  (** Session number: how many nodes went through symbolic execution *)
   ; stats: Stats.t
   ; status: Status.t
   ; proc_desc: Procdesc.t
diff --git a/infer/src/biabduction/interproc.ml b/infer/src/biabduction/interproc.ml
index 5b6e8df96..b476909ce 100644
--- a/infer/src/biabduction/interproc.ml
+++ b/infer/src/biabduction/interproc.ml
@@ -502,7 +502,10 @@ let forward_tabulate summary exe_env tenv proc_cfg wl =
     let curr_node = Worklist.remove wl in
     mark_visited summary curr_node ;
     (* mark nodes visited in fp and re phases *)
-    let session = incr summary.Summary.sessions ; !(summary.Summary.sessions) in
+    let session =
+      summary.Summary.sessions <- summary.Summary.sessions + 1 ;
+      summary.Summary.sessions
+    in
     do_before_node session curr_node ;
     do_node_and_handle curr_node session
   done ;