diff --git a/.clang-format b/.clang-format
index ca08a86..449a149 100644
--- a/.clang-format
+++ b/.clang-format
@@ -21,6 +21,7 @@ AlwaysBreakTemplateDeclarations: true
 BinPackArguments: false
 BinPackParameters: false
 BraceWrapping:
+  AfterCaseLabel:  true
   AfterClass:      true
   AfterControlStatement: true
   AfterEnum:       true
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 67b2ef0..ae939a9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,15 +35,12 @@ endmacro()
 
 macro(clangformat_targets)
   # The clang-format tool is installed under a variety of different names.  Try
-  # to find a sensible one.  Only look for versions 6 to 8 explicitly - we don't
+  # to find a sensible one.  Only look for versions 9 explicitly - we don't
   # know whether our clang-format file will work with newer versions of the
-  # tool
+  # tool.  It does not work with older versions as AfterCaseLabel is not supported
+  # in earlier versions.
   find_program(CLANG_FORMAT NAMES
-    clang-format-8
-    clang-format-7.0
-    clang-format-6.0
-    clang-format70
-    clang-format60
+    clang-format-9
     clang-format)
 
   # If we've found a clang-format tool, generate a target for it, otherwise emit
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 2290c28..14004fb 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -225,15 +225,15 @@ jobs:
 - job: 
   displayName: Format
   pool:
-    vmImage: 'ubuntu-16.04'
+    vmImage: 'ubuntu-18.04'
   steps:
   - script: |
       set -eo pipefail
       wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-      sudo add-apt-repository "deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main"
+      sudo apt-add-repository "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main"
       sudo apt-get update
-      sudo apt-get install -y clang-format-8 clang-tidy-8
-      sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-8 100
+      sudo apt-get install -y clang-format-9 clang-tidy-9
+      sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-9 100
 
     displayName: 'Install clang'
 
@@ -245,7 +245,6 @@ jobs:
   - script: |
       set -eo pipefail
       make clangformat
-      git diff
       git diff --exit-code $(Build.SourceVersion)
 
     workingDirectory: build
@@ -254,7 +253,6 @@ jobs:
 
   - script: |
       set -eo pipefail
-      clang-tidy-8  src/override/malloc.cc  -header-filter="`pwd`/*" -export-fixes=tidy.fail -- -std=c++17 -mcx16
-      if [ -f tidy.fail ] ; then exit 1 ; fi
+      clang-tidy-9  src/override/malloc.cc  -header-filter="`pwd`/*" -warnings-as-errors='*' -export-fixes=tidy.fail -- -std=c++17 -mcx16
 
     displayName: 'Clang-Tidy'
diff --git a/src/ds/address.h b/src/ds/address.h
index 4b61e50..ae98de3 100644
--- a/src/ds/address.h
+++ b/src/ds/address.h
@@ -61,7 +61,7 @@ namespace snmalloc
    * power of two.
    */
   template<size_t alignment, typename T = void>
-  inline T* pointer_align_down(void* p)
+  SNMALLOC_FAST_PATH T* pointer_align_down(void* p)
   {
     static_assert(alignment > 0);
     static_assert(bits::next_pow2_const(alignment) == alignment);
diff --git a/src/ds/bits.h b/src/ds/bits.h
index 91920d1..374dccd 100644
--- a/src/ds/bits.h
+++ b/src/ds/bits.h
@@ -54,7 +54,7 @@ namespace snmalloc
 
     static constexpr size_t ADDRESS_BITS = is64() ? 48 : 32;
 
-    inline size_t clz(size_t x)
+    SNMALLOC_FAST_PATH size_t clz(size_t x)
     {
 #if defined(_MSC_VER)
 #  ifdef USE_LZCNT
@@ -193,7 +193,7 @@ namespace snmalloc
 #endif
     }
 
-    inline size_t next_pow2(size_t x)
+    SNMALLOC_FAST_PATH size_t next_pow2(size_t x)
     {
       // Correct for numbers [0..MAX_SIZE >> 1).
       // Returns 1 for x > (MAX_SIZE >> 1).
@@ -223,7 +223,7 @@ namespace snmalloc
       return BITS - clz_const(x - 1);
     }
 
-    static inline size_t align_down(size_t value, size_t alignment)
+    static SNMALLOC_FAST_PATH size_t align_down(size_t value, size_t alignment)
     {
       assert(next_pow2(alignment) == alignment);
 
diff --git a/src/mem/slab.h b/src/mem/slab.h
index 00058ae..9fa2137 100644
--- a/src/mem/slab.h
+++ b/src/mem/slab.h
@@ -45,6 +45,7 @@ namespace snmalloc
       assert(rsize == sizeclass_to_size(meta.sizeclass));
       assert(sl.get_head() == (SlabLink*)pointer_offset(this, meta.link));
       assert(!meta.is_full());
+      meta.debug_slab_invariant(this);
 
       void* p = nullptr;
       bool p_has_value = false;
@@ -156,7 +157,6 @@ namespace snmalloc
       if (meta.is_unused())
         error("Detected potential double free.");
 #endif
-      meta.debug_slab_invariant(this);
 
       if (unlikely(meta.return_object()))
         return false;
@@ -170,7 +170,7 @@ namespace snmalloc
 
       // Set the next pointer to the previous head.
       Metaslab::store_next(p, head);
-      meta.debug_slab_invariant(this);
+
       return true;
     }
 
@@ -182,6 +182,7 @@ namespace snmalloc
     dealloc_slow(SlabList* sl, Superslab* super, void* p)
     {
       Metaslab& meta = super->get_meta(this);
+      meta.debug_slab_invariant(this);
 
       if (meta.is_full())
       {