diff --git a/source/m3_compile.c b/source/m3_compile.c
index 3fa533a..d253fec 100644
--- a/source/m3_compile.c
+++ b/source/m3_compile.c
@@ -933,7 +933,7 @@ M3Result  FindReferencedLocalWithinCurrentBlock  (IM3Compilation o, u16 * o_pres
     M3Result result = m3Err_none;
 
     IM3CompilationScope scope = & o->block;
-    i16 startIndex = scope->blockStackIndex;
+    u16 startIndex = scope->blockStackIndex;
 
     while (scope->opcode == c_waOp_block)
     {
@@ -1874,7 +1874,7 @@ _   (ReadBlockType (o, & blockType));
 
                     if (IsConstantSlot (o, slot))
                     {
-                        u16 newSlot;
+                        u16 newSlot = c_slotUnused;
 _                       (AllocateSlots (o, & newSlot, type));
 _                       (CopyStackIndexToSlot (o, newSlot, i));
                         o->wasmStack [i] = newSlot;
diff --git a/source/m3_compile.h b/source/m3_compile.h
index 52f7ab2..d4a6733 100644
--- a/source/m3_compile.h
+++ b/source/m3_compile.h
@@ -59,7 +59,7 @@ typedef struct M3CompilationScope
     pc_t                            patches;
     i32                             depth;
     u16                             exitStackIndex;
-    i16                             blockStackIndex;
+    u16                             blockStackIndex;
 //    u16                             topSlot;
     IM3FuncType                     type;
     m3opcode_t                      opcode;
diff --git a/source/m3_info.c b/source/m3_info.c
index f8c0a58..5be93b6 100644
--- a/source/m3_info.c
+++ b/source/m3_info.c
@@ -356,7 +356,7 @@ void  dump_type_stack  (IM3Compilation o)
     {
         d_m3Log(stack, "        ");
 
-        for (u32 i = 0; i < o->stackIndex; ++i)
+        for (u16 i = 0; i < o->stackIndex; ++i)
         {
             if (i > 0 and i == o->stackFirstDynamicIndex)
                 printf ("#");