diff --git a/src/conf.h b/src/conf.h
index 5df890ea..854ea167 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -88,7 +88,7 @@
 
 
 #if !defined(WITH_UCL)
-#  error "you lose"
+#  error "please set UCLDIR in the Makefile"
 #endif
 #if defined(WITH_UCL)
 #  include <ucl/uclconf.h>
diff --git a/src/main.cpp b/src/main.cpp
index 00c1275e..42aa1706 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1039,7 +1039,10 @@ void upx_sanity_check(void)
     COMPILE_TIME_ASSERT(__alignof__(LE32) == 1);
 #endif
 
-#if !defined(__WATCOMC__)
+    COMPILE_TIME_ASSERT((((unsigned)1    << 31) >> 31) == 1);
+    COMPILE_TIME_ASSERT((((upx_uint64l)1 << 63) >> 63) == 1);
+
+#if !defined(__WATCOMC__)   // Watcom C does not support inner classes
     struct align_assertion_1a_t
     {
         struct foo_t {