diff --git a/streamline.cm b/streamline.cm
index ae1e0048..bb4c2c9e 100644
--- a/streamline.cm
+++ b/streamline.cm
@@ -457,6 +457,19 @@ var streamline = function(ir, log) {
           i = i + 1
           continue
         }
+        if (op == "get" && func._closure_slot_types != null) {
+          slot = instr[1]
+          typ = T_UNKNOWN
+          src_typ = func._closure_slot_types[text(instr[2]) + "_" + text(instr[3])]
+          if (src_typ != null) {
+            typ = src_typ
+          }
+          if (slot > 0 && slot > nr_args) {
+            merge_backward(write_types, slot, typ)
+          }
+          i = i + 1
+          continue
+        }
 
         rule = write_rules[op]
         if (rule != null) {
@@ -1966,6 +1979,71 @@ var streamline = function(ir, log) {
       }
       fi = fi + 1
     }
+    ir._parent_of = parent_of
+    ir._parent_fc = fc
+    return null
+  }
+
+  // =========================================================
+  // Resolve closure slot types from parent write_types.
+  // For each `get` in func, walk the parent chain and look up
+  // the ancestor's inferred write type for that closure slot.
+  // =========================================================
+  var resolve_closure_types = function(func, fi, ir) {
+    var parent_of = ir._parent_of
+    var fc = ir._parent_fc
+    var instructions = func.instructions
+    var num_instr = 0
+    var closure_types = null
+    var i = 0
+    var instr = null
+    var slot = 0
+    var depth = 0
+    var anc = 0
+    var j = 0
+    var target = null
+    var typ = null
+    var key = null
+
+    if (instructions == null || parent_of == null) {
+      return null
+    }
+
+    num_instr = length(instructions)
+    closure_types = {}
+    i = 0
+    while (i < num_instr) {
+      instr = instructions[i]
+      if (is_array(instr) && instr[0] == "get") {
+        slot = instr[2]
+        depth = instr[3]
+        key = text(slot) + "_" + text(depth)
+        if (closure_types[key] == null) {
+          anc = fi
+          j = 0
+          while (j < depth && anc >= 0) {
+            anc = parent_of[anc]
+            j = j + 1
+          }
+          if (anc >= 0) {
+            if (anc == fc) {
+              target = ir.main
+            } else {
+              target = ir.functions[anc]
+            }
+            if (target != null && target._write_types != null) {
+              typ = target._write_types[slot]
+              if (typ != null) {
+                closure_types[key] = typ
+              }
+            }
+          }
+        }
+      }
+      i = i + 1
+    }
+
+    func._closure_slot_types = closure_types
     return null
   }
 
@@ -2284,6 +2362,7 @@ var streamline = function(ir, log) {
 
     run_cycle("")
     run_cycle("_2")
+    func._write_types = write_types
     if (ir._warn) {
       diagnose_function(func, {param_types: param_types, write_types: write_types}, ir)
     }
@@ -2305,11 +2384,12 @@ var streamline = function(ir, log) {
     optimize_function(ir.main, log)
   }
 
-  // Process all sub-functions
+  // Process all sub-functions (resolve closure types from parent first)
   var fi = 0
   if (ir.functions != null) {
     fi = 0
     while (fi < length(ir.functions)) {
+      resolve_closure_types(ir.functions[fi], fi, ir)
       optimize_function(ir.functions[fi], log)
       fi = fi + 1
     }