diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index ee59d9eea426..b8be02bcba46 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -363,7 +363,7 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         if alloc.kind != kind {
             return Err(EvalError::DeallocatedWrongMemoryKind(alloc.kind, kind));
         }
-        if !alloc.locks.is_empty() {
+        if alloc.locks.values().any(|locks| !locks.is_empty()) {
             return Err(EvalError::DeallocatedLockedMemory);
         }
         if let Some((size, align)) = size_and_align {
@@ -524,7 +524,7 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
 
     /// Acquire the lock for the given lifetime
     pub(crate) fn acquire_lock(&mut self, ptr: MemoryPointer, len: u64, region: Option<CodeExtent>, kind: AccessKind) -> EvalResult<'tcx> {
-        trace!("Acquiring {:?} lock at {:?}, size {}", kind, ptr, len);
+        trace!("Acquiring {:?} lock at {:?}, size {} for region {:?}", kind, ptr, len, region);
         if len == 0 {
             return Ok(());
         }
@@ -536,9 +536,9 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         Ok(())
     }
 
-    /// Release a lock prematurely
+    /// Release a write lock prematurely
     pub(crate) fn release_lock_until(&mut self, ptr: MemoryPointer, len: u64, release_until: Option<CodeExtent>) -> EvalResult<'tcx> {
-        // TODO: More tracing.
+        trace!("Releasing write lock at {:?}, size {} until {:?}", ptr, len, release_until);
         // Make sure there are no read locks and no *other* write locks here
         if let Err(_) = self.check_locks(ptr, len, AccessKind::Write) {
             return Err(EvalError::InvalidMemoryLockRelease { ptr, len });
@@ -565,7 +565,7 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
     }
 
     pub(crate) fn locks_lifetime_ended(&mut self, ending_region: Option<CodeExtent>) {
-        // TODO: More tracing.
+        trace!("Releasing locks that expire at {:?}", ending_region);
         let cur_frame = self.cur_frame;
         let has_ended =  |lock: &LockInfo| -> bool {
             if lock.lifetime.frame != cur_frame {
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index f148a096128a..4f7eb8eb6cc1 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -7,8 +7,9 @@ use rustc::hir;
 use rustc::mir::visit::{Visitor, LvalueContext};
 use rustc::mir;
 use rustc::traits::Reveal;
+use rustc::ty;
 use rustc::ty::layout::Layout;
-use rustc::ty::{subst, self};
+use rustc::ty::subst::{Subst, Substs};
 
 use error::{EvalResult, EvalError};
 use eval_context::{EvalContext, StackPopCleanup};
@@ -133,12 +134,13 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             // Validity checks.
             Validate(ref op, ref lvalues) => {
                 for operand in lvalues {
+                    // We need to monomorphize ty *without* erasing lifetimes
+                    let ty = operand.ty.subst(self.tcx, self.substs());
+                    // TODO: do we have to self.tcx.normalize_associated_type(&{ty}) ?  That however seems to erase lifetimes.
                     let lvalue = self.eval_lvalue(&operand.lval)?;
-                    self.validate(lvalue, operand.ty, ValidationCtx::new(*op))?;
+                    self.validate(lvalue, ty, ValidationCtx::new(*op))?;
                 }
             }
-
-            // Just a borrowck thing
             EndRegion(ce) => {
                 self.memory.locks_lifetime_ended(Some(ce));
             }
@@ -180,7 +182,7 @@ impl<'a, 'b, 'tcx> ConstantExtractor<'a, 'b, 'tcx> {
     fn global_item(
         &mut self,
         def_id: DefId,
-        substs: &'tcx subst::Substs<'tcx>,
+        substs: &'tcx Substs<'tcx>,
         span: Span,
         mutability: Mutability,
     ) {