diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index 6454c764127..bb5f944fa36 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -1552,6 +1552,38 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }
         }
     }
+
+    /// convenience function to ensure correct usage of globals and code-sharing with locals
+    pub fn modify_global<
+        F: FnOnce(&mut Self, Option<Value>) -> EvalResult<'tcx, Value>,
+    >(
+        &mut self,
+        cid: GlobalId<'tcx>,
+        f: F,
+    ) -> EvalResult<'tcx, ()> {
+        let mut val = *self.globals.get(&cid).expect("global not cached");
+        if !val.mutable {
+            return Err(EvalError::ModifiedConstantMemory);
+        }
+        val.data = Some(f(self, val.data)?);
+        *self.globals.get_mut(&cid).expect("already checked") = val;
+        Ok(())
+    }
+
+    /// convenience function to ensure correct usage of locals and code-sharing with globals
+    pub fn modify_local<
+        F: FnOnce(&mut Self, Option<Value>) -> EvalResult<'tcx, Value>,
+    >(
+        &mut self,
+        frame: usize,
+        local: mir::Local,
+        f: F,
+    ) -> EvalResult<'tcx, ()> {
+        let val = self.stack[frame].get_local(local);
+        let val = f(self, val)?;
+        self.stack[frame].set_local(local, val);
+        Ok(())
+    }
 }
 
 impl<'tcx> Frame<'tcx> {
diff --git a/src/interpreter/terminator/intrinsics.rs b/src/interpreter/terminator/intrinsics.rs
index 2b10f825038..dfa4a427e90 100644
--- a/src/interpreter/terminator/intrinsics.rs
+++ b/src/interpreter/terminator/intrinsics.rs
@@ -127,52 +127,32 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
 
             "init" => {
                 let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
-                match dest {
-                    Lvalue::Local { frame, local } => {
-                        match self.stack[frame].get_local(local) {
-                            Some(Value::ByRef(ptr)) => self.memory.write_repeat(ptr, 0, size)?,
-                            None => match self.ty_to_primval_kind(dest_ty) {
-                                Ok(kind) => self.stack[frame].set_local(local, Value::ByVal(PrimVal::new(0, kind))),
-                                Err(_) => {
-                                    let ptr = self.alloc_ptr_with_substs(dest_ty, substs)?;
-                                    self.memory.write_repeat(ptr, 0, size)?;
-                                    self.stack[frame].set_local(local, Value::ByRef(ptr));
-                                }
-                            },
-                            Some(Value::ByVal(val)) => self.stack[frame].set_local(local, Value::ByVal(PrimVal::new(0, val.kind))),
-                            Some(Value::ByValPair(a, b)) => self.stack[frame].set_local(local, Value::ByValPair(
-                                PrimVal::new(0, a.kind),
-                                PrimVal::new(0, b.kind),
-                            )),
-                        }
+                let init = |this: &mut Self, val: Option<Value>| {
+                    match val {
+                        Some(Value::ByRef(ptr)) => {
+                            this.memory.write_repeat(ptr, 0, size)?;
+                            Ok(Value::ByRef(ptr))
+                        },
+                        None => match this.ty_to_primval_kind(dest_ty) {
+                            Ok(kind) => Ok(Value::ByVal(PrimVal::new(0, kind))),
+                            Err(_) => {
+                                let ptr = this.alloc_ptr_with_substs(dest_ty, substs)?;
+                                this.memory.write_repeat(ptr, 0, size)?;
+                                Ok(Value::ByRef(ptr))
+                            }
+                        },
+                        Some(Value::ByVal(value)) => Ok(Value::ByVal(PrimVal::new(0, value.kind))),
+                        Some(Value::ByValPair(a, b)) => Ok(Value::ByValPair(
+                            PrimVal::new(0, a.kind),
+                            PrimVal::new(0, b.kind),
+                        )),
                     }
+                };
+                match dest {
+                    Lvalue::Local { frame, local } => self.modify_local(frame, local, init)?,
                     Lvalue::Ptr { ptr, extra: LvalueExtra::None } => self.memory.write_repeat(ptr, 0, size)?,
                     Lvalue::Ptr { .. } => bug!("init intrinsic tried to write to fat ptr target"),
-                    Lvalue::Global(cid) => {
-                        let global_val = *self.globals.get(&cid).expect("global not cached");
-                        if !global_val.mutable {
-                            return Err(EvalError::ModifiedConstantMemory);
-                        }
-                        match global_val.data {
-                            Some(Value::ByRef(ptr)) => self.memory.write_repeat(ptr, 0, size)?,
-                            None => match self.ty_to_primval_kind(dest_ty) {
-                                Ok(kind) => self.globals
-                                                .get_mut(&cid)
-                                                .expect("already checked")
-                                                .data = Some(Value::ByVal(PrimVal::new(0, kind))),
-                                Err(_) => {
-                                    let ptr = self.alloc_ptr_with_substs(dest_ty, substs)?;
-                                    self.memory.write_repeat(ptr, 0, size)?;
-                                    self.globals.get_mut(&cid).expect("already checked").data = Some(Value::ByRef(ptr));
-                                },
-                            },
-                            Some(Value::ByVal(val)) => self.globals.get_mut(&cid).expect("already checked").data = Some(Value::ByVal(PrimVal::new(0, val.kind))),
-                            Some(Value::ByValPair(a, b)) => self.globals.get_mut(&cid).expect("already checked").data = Some(Value::ByValPair(
-                                PrimVal::new(0, a.kind),
-                                PrimVal::new(0, b.kind),
-                            )),
-                        }
-                    }
+                    Lvalue::Global(cid) => self.modify_global(cid, init)?,
                 }
             }