diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index 827ab6ee70d7..a69d6b944059 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -1594,7 +1594,7 @@ pub fn alloca_maybe_zeroed(cx: @Block, ty: Type, name: &str, zero: bool) -> Valu
     let p = Alloca(cx, ty, name);
     if zero {
         let b = cx.fcx.ccx.builder();
-        b.position_before(cx.fcx.alloca_insert_pt.unwrap());
+        b.position_before(cx.fcx.alloca_insert_pt.get().unwrap());
         memzero(&b, p, ty);
     }
     p
@@ -1687,7 +1687,7 @@ pub fn new_fn_ctxt_w_id(ccx: @CrateContext,
           },
           llretptr: Cell::new(None),
           entry_bcx: None,
-          alloca_insert_pt: None,
+          alloca_insert_pt: Cell::new(None),
           llreturn: None,
           llself: None,
           personality: None,
@@ -1711,7 +1711,8 @@ pub fn new_fn_ctxt_w_id(ccx: @CrateContext,
         Load(entry_bcx, C_null(Type::i8p()));
 
         fcx.entry_bcx = Some(entry_bcx);
-        fcx.alloca_insert_pt = Some(llvm::LLVMGetFirstInstruction(entry_bcx.llbb));
+        fcx.alloca_insert_pt.set(Some(
+                llvm::LLVMGetFirstInstruction(entry_bcx.llbb)));
     }
 
     if !ty::type_is_voidish(ccx.tcx, substd_output_type) {
diff --git a/src/librustc/middle/trans/build.rs b/src/librustc/middle/trans/build.rs
index ba39c869ab00..faf210c1a9ea 100644
--- a/src/librustc/middle/trans/build.rs
+++ b/src/librustc/middle/trans/build.rs
@@ -314,7 +314,7 @@ pub fn Alloca(cx: &Block, Ty: Type, name: &str) -> ValueRef {
     unsafe {
         if cx.unreachable.get() { return llvm::LLVMGetUndef(Ty.ptr_to().to_ref()); }
         let b = cx.fcx.ccx.builder();
-        b.position_before(cx.fcx.alloca_insert_pt.unwrap());
+        b.position_before(cx.fcx.alloca_insert_pt.get().unwrap());
         b.alloca(Ty, name)
     }
 }
@@ -323,7 +323,7 @@ pub fn ArrayAlloca(cx: &Block, Ty: Type, Val: ValueRef) -> ValueRef {
     unsafe {
         if cx.unreachable.get() { return llvm::LLVMGetUndef(Ty.ptr_to().to_ref()); }
         let b = cx.fcx.ccx.builder();
-        b.position_before(cx.fcx.alloca_insert_pt.unwrap());
+        b.position_before(cx.fcx.alloca_insert_pt.get().unwrap());
         b.array_alloca(Ty, Val)
     }
 }
diff --git a/src/librustc/middle/trans/common.rs b/src/librustc/middle/trans/common.rs
index 199a2b18d753..79b7545b9bc4 100644
--- a/src/librustc/middle/trans/common.rs
+++ b/src/librustc/middle/trans/common.rs
@@ -221,7 +221,7 @@ pub struct FunctionContext {
     // the function, due to LLVM's quirks.
     // A marker for the place where we want to insert the function's static
     // allocas, so that LLVM will coalesce them into a single alloca call.
-    alloca_insert_pt: Option<ValueRef>,
+    alloca_insert_pt: Cell<Option<ValueRef>>,
     llreturn: Option<BasicBlockRef>,
     // The 'self' value currently in use in this function, if there
     // is one.
@@ -291,7 +291,9 @@ impl FunctionContext {
 
     pub fn cleanup(&mut self) {
         unsafe {
-            llvm::LLVMInstructionEraseFromParent(self.alloca_insert_pt.unwrap());
+            llvm::LLVMInstructionEraseFromParent(self.alloca_insert_pt
+                                                     .get()
+                                                     .unwrap());
         }
         // Remove the cycle between fcx and bcx, so memory can be freed
         self.entry_bcx = None;