diff --git a/src/hb-aat-layout-common.hh b/src/hb-aat-layout-common.hh
index 85332b0f76fa48fdcbda80af87d685e6bf3f35b3..431a12bc7a676569d04bfc7dd8281ddd64f51a07 100644
--- a/src/hb-aat-layout-common.hh
+++ b/src/hb-aat-layout-common.hh
@@ -77,7 +77,7 @@ struct LookupFormat0
 template <typename T>
 struct LookupSegmentSingle
 {
-  enum { TerminationWordCount = 2 };
+  enum { TerminationWordCount = 2u };
 
   int cmp (hb_codepoint_t g) const
   { return g < first ? -1 : g <= last ? 0 : +1 ; }
@@ -136,7 +136,7 @@ struct LookupFormat2
 template <typename T>
 struct LookupSegmentArray
 {
-  enum { TerminationWordCount = 2 };
+  enum { TerminationWordCount = 2u };
 
   const T* get_value (hb_codepoint_t glyph_id, const void *base) const
   {
@@ -207,7 +207,7 @@ struct LookupFormat4
 template <typename T>
 struct LookupSingle
 {
-  enum { TerminationWordCount = 1 };
+  enum { TerminationWordCount = 1u };
 
   int cmp (hb_codepoint_t g) const { return glyph.cmp (g); }
 
diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index 8a3170ca9a5a6705b9ebcb1f861c34ae65fc72d7..ab963a5fbe608a8bc649e23d24c6e3500048c506 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -119,7 +119,7 @@ struct hb_buffer_t
   /* Text before / after the main buffer contents.
    * Always in Unicode, and ordered outward.
    * Index 0 is for "pre-context", 1 for "post-context". */
-  enum { CONTEXT_LENGTH = 5 };
+  enum { CONTEXT_LENGTH = 5u };
   hb_codepoint_t context[2][CONTEXT_LENGTH];
   unsigned int context_len[2];
 
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 672d4ee2e6a163dd2943a028a16f5816415c91c3..179db6523844363010016611d63fe6ccd7db04c6 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1299,7 +1299,7 @@ hb_ot_layout_feature_get_characters (hb_face_t      *face,
 
 struct GSUBProxy
 {
-  enum { table_index = 0 };
+  enum { table_index = 0u };
   enum { inplace = false };
   typedef OT::SubstLookup Lookup;
 
@@ -1313,7 +1313,7 @@ struct GSUBProxy
 
 struct GPOSProxy
 {
-  enum { table_index = 1 };
+  enum { table_index = 1u };
   enum { inplace = true };
   typedef OT::PosLookup Lookup;
 
@@ -1387,7 +1387,7 @@ apply_string (OT::hb_ot_apply_context_t *c,
   if (likely (!lookup.is_reverse ()))
   {
     /* in/out forward substitution/positioning */
-    if (Proxy::table_index == 0)
+    if (Proxy::table_index == 0u)
       buffer->clear_output ();
     buffer->idx = 0;
 
@@ -1404,7 +1404,7 @@ apply_string (OT::hb_ot_apply_context_t *c,
   else
   {
     /* in-place backward substitution/positioning */
-    if (Proxy::table_index == 0)
+    if (Proxy::table_index == 0u)
       buffer->remove_output ();
     buffer->idx = buffer->len - 1;