diff --git a/example/finalize.c b/example/finalize.c
index 6841617..8a342d7 100644
--- a/example/finalize.c
+++ b/example/finalize.c
@@ -10,7 +10,7 @@
 const int iterations = 100000;
 
 void finalize(void* data) {
-  int i = (int)data;
+  int i = (intptr_t)data;
   if (i % (iterations / 10) == 0) printf("Finalizing #%d...\n", i);
 }
 
diff --git a/src/wasm-bin.cc b/src/wasm-bin.cc
index d43a3a1..b3036e1 100644
--- a/src/wasm-bin.cc
+++ b/src/wasm-bin.cc
@@ -82,7 +82,7 @@ void encode_const_zero(char*& ptr, const ValType* type) {
     case F64: *ptr++ = 0x44; break;
     default: assert(false);
   }
-  for (int i = 0; i < zero_size(type); ++i) *ptr++ = 0;
+  for (size_t i = 0; i < zero_size(type); ++i) *ptr++ = 0;
 }
 
 
@@ -123,7 +123,7 @@ auto wrapper(const FuncType* type) -> vec<byte_t> {
   *ptr++ = 0x00;  // func
   *ptr++ = 0;  // func index
 
-  assert(ptr - binary.get() == size);
+  assert(static_cast<size_t>(ptr - binary.get()) == size);
   return binary;
 }
 
@@ -149,7 +149,7 @@ auto wrapper(const GlobalType* type) -> vec<byte_t> {
   *ptr++ = 0x03;  // global
   *ptr++ = 0;  // func index
 
-  assert(ptr - binary.get() == size);
+  assert(static_cast<size_t>(ptr - binary.get()) == size);
   return binary;
 }
 
diff --git a/src/wasm-v8.cc b/src/wasm-v8.cc
index c46ff09..8d0a246 100644
--- a/src/wasm-v8.cc
+++ b/src/wasm-v8.cc
@@ -605,6 +605,7 @@ auto ExternType::copy() const -> own<ExternType*> {
     case EXTERN_GLOBAL: return global()->copy();
     case EXTERN_TABLE: return table()->copy();
     case EXTERN_MEMORY: return memory()->copy();
+    default: assert(false);
   }
 }
 
@@ -1100,6 +1101,7 @@ auto v8_to_val(
         UNIMPLEMENTED("ref value");
       }
     }
+    default: assert(false);
   }
 }
 
@@ -1550,6 +1552,7 @@ auto Extern::type() const -> own<ExternType*> {
     case EXTERN_GLOBAL: return global()->type();
     case EXTERN_TABLE: return table()->type();
     case EXTERN_MEMORY: return memory()->type();
+    default: assert(false);
   }
 }
 
@@ -1794,7 +1797,7 @@ void FuncData::v8_callback(const v8::FunctionCallbackInfo<v8::Value>& info) {
   auto& param_types = self->type->params();
   auto& result_types = self->type->results();
 
-  assert(param_types.size() == info.Length());
+  assert(param_types.size() == static_cast<size_t>(info.Length()));
 
   // TODO: cache params and result arrays per thread.
   auto args = std::unique_ptr<Val[]>(new Val[param_types.size()]);
@@ -2194,6 +2197,7 @@ auto Instance::exports() const -> vec<Extern*> {
         assert(wasm_v8::extern_kind(obj) == wasm_v8::EXTERN_MEMORY);
         exports[i].reset(RefImpl<Memory>::make(store, obj));
       } break;
+      default: assert(false);
     }
   }