diff --git a/common.mk b/common.mk
old mode 100755
new mode 100644
index 8f123e54c6..b94be35d47
--- a/common.mk
+++ b/common.mk
@@ -1533,6 +1533,7 @@ addr2line.$(OBJEXT): {$(VPATH)}missing.h
 array.$(OBJEXT): $(hdrdir)/ruby.h
 array.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 array.$(OBJEXT): {$(VPATH)}array.c
+array.$(OBJEXT): {$(VPATH)}assert.h
 array.$(OBJEXT): {$(VPATH)}config.h
 array.$(OBJEXT): {$(VPATH)}debug_counter.h
 array.$(OBJEXT): {$(VPATH)}defines.h
@@ -1558,6 +1559,7 @@ ast.$(OBJEXT): $(CCAN_DIR)/list/list.h
 ast.$(OBJEXT): $(CCAN_DIR)/str/str.h
 ast.$(OBJEXT): $(hdrdir)/ruby.h
 ast.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+ast.$(OBJEXT): {$(VPATH)}assert.h
 ast.$(OBJEXT): {$(VPATH)}ast.c
 ast.$(OBJEXT): {$(VPATH)}config.h
 ast.$(OBJEXT): {$(VPATH)}defines.h
@@ -1582,6 +1584,7 @@ ast.$(OBJEXT): {$(VPATH)}vm_core.h
 ast.$(OBJEXT): {$(VPATH)}vm_opts.h
 bignum.$(OBJEXT): $(hdrdir)/ruby.h
 bignum.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+bignum.$(OBJEXT): {$(VPATH)}assert.h
 bignum.$(OBJEXT): {$(VPATH)}bignum.c
 bignum.$(OBJEXT): {$(VPATH)}config.h
 bignum.$(OBJEXT): {$(VPATH)}defines.h
@@ -1604,6 +1607,7 @@ class.$(OBJEXT): $(CCAN_DIR)/list/list.h
 class.$(OBJEXT): $(CCAN_DIR)/str/str.h
 class.$(OBJEXT): $(hdrdir)/ruby.h
 class.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+class.$(OBJEXT): {$(VPATH)}assert.h
 class.$(OBJEXT): {$(VPATH)}class.c
 class.$(OBJEXT): {$(VPATH)}config.h
 class.$(OBJEXT): {$(VPATH)}constant.h
@@ -1643,6 +1647,7 @@ compile.$(OBJEXT): $(CCAN_DIR)/list/list.h
 compile.$(OBJEXT): $(CCAN_DIR)/str/str.h
 compile.$(OBJEXT): $(hdrdir)/ruby.h
 compile.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+compile.$(OBJEXT): {$(VPATH)}assert.h
 compile.$(OBJEXT): {$(VPATH)}compile.c
 compile.$(OBJEXT): {$(VPATH)}config.h
 compile.$(OBJEXT): {$(VPATH)}defines.h
@@ -1680,6 +1685,7 @@ compile.$(OBJEXT): {$(VPATH)}vm_debug.h
 compile.$(OBJEXT): {$(VPATH)}vm_opts.h
 complex.$(OBJEXT): $(hdrdir)/ruby.h
 complex.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+complex.$(OBJEXT): {$(VPATH)}assert.h
 complex.$(OBJEXT): {$(VPATH)}complex.c
 complex.$(OBJEXT): {$(VPATH)}config.h
 complex.$(OBJEXT): {$(VPATH)}defines.h
@@ -1701,6 +1707,7 @@ cont.$(OBJEXT): $(CCAN_DIR)/str/str.h
 cont.$(OBJEXT): $(hdrdir)/ruby.h
 cont.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 cont.$(OBJEXT): {$(VPATH)}$(COROUTINE_H)
+cont.$(OBJEXT): {$(VPATH)}assert.h
 cont.$(OBJEXT): {$(VPATH)}config.h
 cont.$(OBJEXT): {$(VPATH)}cont.c
 cont.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -1733,6 +1740,7 @@ debug.$(OBJEXT): $(CCAN_DIR)/list/list.h
 debug.$(OBJEXT): $(CCAN_DIR)/str/str.h
 debug.$(OBJEXT): $(hdrdir)/ruby.h
 debug.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+debug.$(OBJEXT): {$(VPATH)}assert.h
 debug.$(OBJEXT): {$(VPATH)}config.h
 debug.$(OBJEXT): {$(VPATH)}debug.c
 debug.$(OBJEXT): {$(VPATH)}defines.h
@@ -1867,6 +1875,7 @@ enc/utf_8.$(OBJEXT): {$(VPATH)}oniguruma.h
 enc/utf_8.$(OBJEXT): {$(VPATH)}regenc.h
 encoding.$(OBJEXT): $(hdrdir)/ruby.h
 encoding.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+encoding.$(OBJEXT): {$(VPATH)}assert.h
 encoding.$(OBJEXT): {$(VPATH)}config.h
 encoding.$(OBJEXT): {$(VPATH)}defines.h
 encoding.$(OBJEXT): {$(VPATH)}encindex.h
@@ -1922,6 +1931,7 @@ error.$(OBJEXT): $(CCAN_DIR)/list/list.h
 error.$(OBJEXT): $(CCAN_DIR)/str/str.h
 error.$(OBJEXT): $(hdrdir)/ruby.h
 error.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+error.$(OBJEXT): {$(VPATH)}assert.h
 error.$(OBJEXT): {$(VPATH)}config.h
 error.$(OBJEXT): {$(VPATH)}defines.h
 error.$(OBJEXT): {$(VPATH)}encoding.h
@@ -1951,6 +1961,7 @@ eval.$(OBJEXT): $(CCAN_DIR)/list/list.h
 eval.$(OBJEXT): $(CCAN_DIR)/str/str.h
 eval.$(OBJEXT): $(hdrdir)/ruby.h
 eval.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+eval.$(OBJEXT): {$(VPATH)}assert.h
 eval.$(OBJEXT): {$(VPATH)}config.h
 eval.$(OBJEXT): {$(VPATH)}debug_counter.h
 eval.$(OBJEXT): {$(VPATH)}defines.h
@@ -2012,6 +2023,7 @@ gc.$(OBJEXT): $(CCAN_DIR)/list/list.h
 gc.$(OBJEXT): $(CCAN_DIR)/str/str.h
 gc.$(OBJEXT): $(hdrdir)/ruby.h
 gc.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+gc.$(OBJEXT): {$(VPATH)}assert.h
 gc.$(OBJEXT): {$(VPATH)}config.h
 gc.$(OBJEXT): {$(VPATH)}constant.h
 gc.$(OBJEXT): {$(VPATH)}debug.h
@@ -2057,6 +2069,7 @@ golf_prelude.$(OBJEXT): $(CCAN_DIR)/list/list.h
 golf_prelude.$(OBJEXT): $(CCAN_DIR)/str/str.h
 golf_prelude.$(OBJEXT): $(hdrdir)/ruby.h
 golf_prelude.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+golf_prelude.$(OBJEXT): {$(VPATH)}assert.h
 golf_prelude.$(OBJEXT): {$(VPATH)}config.h
 golf_prelude.$(OBJEXT): {$(VPATH)}defines.h
 golf_prelude.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2096,6 +2109,7 @@ goruby.$(OBJEXT): {$(VPATH)}subst.h
 goruby.$(OBJEXT): {$(VPATH)}vm_debug.h
 hash.$(OBJEXT): $(hdrdir)/ruby.h
 hash.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+hash.$(OBJEXT): {$(VPATH)}assert.h
 hash.$(OBJEXT): {$(VPATH)}config.h
 hash.$(OBJEXT): {$(VPATH)}debug_counter.h
 hash.$(OBJEXT): {$(VPATH)}defines.h
@@ -2137,6 +2151,7 @@ io.$(OBJEXT): $(CCAN_DIR)/list/list.h
 io.$(OBJEXT): $(CCAN_DIR)/str/str.h
 io.$(OBJEXT): $(hdrdir)/ruby.h
 io.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+io.$(OBJEXT): {$(VPATH)}assert.h
 io.$(OBJEXT): {$(VPATH)}config.h
 io.$(OBJEXT): {$(VPATH)}defines.h
 io.$(OBJEXT): {$(VPATH)}dln.h
@@ -2168,6 +2183,7 @@ iseq.$(OBJEXT): $(CCAN_DIR)/list/list.h
 iseq.$(OBJEXT): $(CCAN_DIR)/str/str.h
 iseq.$(OBJEXT): $(hdrdir)/ruby.h
 iseq.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+iseq.$(OBJEXT): {$(VPATH)}assert.h
 iseq.$(OBJEXT): {$(VPATH)}config.h
 iseq.$(OBJEXT): {$(VPATH)}debug_counter.h
 iseq.$(OBJEXT): {$(VPATH)}defines.h
@@ -2207,6 +2223,7 @@ load.$(OBJEXT): $(CCAN_DIR)/list/list.h
 load.$(OBJEXT): $(CCAN_DIR)/str/str.h
 load.$(OBJEXT): $(hdrdir)/ruby.h
 load.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+load.$(OBJEXT): {$(VPATH)}assert.h
 load.$(OBJEXT): {$(VPATH)}config.h
 load.$(OBJEXT): {$(VPATH)}defines.h
 load.$(OBJEXT): {$(VPATH)}dln.h
@@ -2323,6 +2340,7 @@ mjit.$(OBJEXT): $(CCAN_DIR)/list/list.h
 mjit.$(OBJEXT): $(CCAN_DIR)/str/str.h
 mjit.$(OBJEXT): $(hdrdir)/ruby.h
 mjit.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+mjit.$(OBJEXT): {$(VPATH)}assert.h
 mjit.$(OBJEXT): {$(VPATH)}config.h
 mjit.$(OBJEXT): {$(VPATH)}constant.h
 mjit.$(OBJEXT): {$(VPATH)}debug.h
@@ -2357,6 +2375,7 @@ mjit_compile.$(OBJEXT): $(CCAN_DIR)/list/list.h
 mjit_compile.$(OBJEXT): $(CCAN_DIR)/str/str.h
 mjit_compile.$(OBJEXT): $(hdrdir)/ruby.h
 mjit_compile.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+mjit_compile.$(OBJEXT): {$(VPATH)}assert.h
 mjit_compile.$(OBJEXT): {$(VPATH)}config.h
 mjit_compile.$(OBJEXT): {$(VPATH)}debug_counter.h
 mjit_compile.$(OBJEXT): {$(VPATH)}defines.h
@@ -2389,6 +2408,7 @@ node.$(OBJEXT): $(CCAN_DIR)/list/list.h
 node.$(OBJEXT): $(CCAN_DIR)/str/str.h
 node.$(OBJEXT): $(hdrdir)/ruby.h
 node.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+node.$(OBJEXT): {$(VPATH)}assert.h
 node.$(OBJEXT): {$(VPATH)}config.h
 node.$(OBJEXT): {$(VPATH)}defines.h
 node.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2492,6 +2512,7 @@ prelude.$(OBJEXT): $(CCAN_DIR)/list/list.h
 prelude.$(OBJEXT): $(CCAN_DIR)/str/str.h
 prelude.$(OBJEXT): $(hdrdir)/ruby.h
 prelude.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+prelude.$(OBJEXT): {$(VPATH)}assert.h
 prelude.$(OBJEXT): {$(VPATH)}config.h
 prelude.$(OBJEXT): {$(VPATH)}defines.h
 prelude.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2523,6 +2544,7 @@ proc.$(OBJEXT): $(CCAN_DIR)/list/list.h
 proc.$(OBJEXT): $(CCAN_DIR)/str/str.h
 proc.$(OBJEXT): $(hdrdir)/ruby.h
 proc.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+proc.$(OBJEXT): {$(VPATH)}assert.h
 proc.$(OBJEXT): {$(VPATH)}config.h
 proc.$(OBJEXT): {$(VPATH)}defines.h
 proc.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2554,6 +2576,7 @@ process.$(OBJEXT): $(CCAN_DIR)/list/list.h
 process.$(OBJEXT): $(CCAN_DIR)/str/str.h
 process.$(OBJEXT): $(hdrdir)/ruby.h
 process.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+process.$(OBJEXT): {$(VPATH)}assert.h
 process.$(OBJEXT): {$(VPATH)}config.h
 process.$(OBJEXT): {$(VPATH)}defines.h
 process.$(OBJEXT): {$(VPATH)}dln.h
@@ -2615,6 +2638,7 @@ range.$(OBJEXT): {$(VPATH)}st.h
 range.$(OBJEXT): {$(VPATH)}subst.h
 rational.$(OBJEXT): $(hdrdir)/ruby.h
 rational.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+rational.$(OBJEXT): {$(VPATH)}assert.h
 rational.$(OBJEXT): {$(VPATH)}config.h
 rational.$(OBJEXT): {$(VPATH)}defines.h
 rational.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2733,6 +2757,7 @@ ruby.$(OBJEXT): $(CCAN_DIR)/str/str.h
 ruby.$(OBJEXT): $(hdrdir)/ruby.h
 ruby.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 ruby.$(OBJEXT): $(hdrdir)/ruby/version.h
+ruby.$(OBJEXT): {$(VPATH)}assert.h
 ruby.$(OBJEXT): {$(VPATH)}config.h
 ruby.$(OBJEXT): {$(VPATH)}debug_counter.h
 ruby.$(OBJEXT): {$(VPATH)}defines.h
@@ -2767,6 +2792,7 @@ safe.$(OBJEXT): $(CCAN_DIR)/list/list.h
 safe.$(OBJEXT): $(CCAN_DIR)/str/str.h
 safe.$(OBJEXT): $(hdrdir)/ruby.h
 safe.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+safe.$(OBJEXT): {$(VPATH)}assert.h
 safe.$(OBJEXT): {$(VPATH)}config.h
 safe.$(OBJEXT): {$(VPATH)}defines.h
 safe.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2805,6 +2831,7 @@ signal.$(OBJEXT): $(CCAN_DIR)/list/list.h
 signal.$(OBJEXT): $(CCAN_DIR)/str/str.h
 signal.$(OBJEXT): $(hdrdir)/ruby.h
 signal.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+signal.$(OBJEXT): {$(VPATH)}assert.h
 signal.$(OBJEXT): {$(VPATH)}config.h
 signal.$(OBJEXT): {$(VPATH)}debug_counter.h
 signal.$(OBJEXT): {$(VPATH)}defines.h
@@ -2882,6 +2909,7 @@ strftime.$(OBJEXT): {$(VPATH)}subst.h
 strftime.$(OBJEXT): {$(VPATH)}timev.h
 string.$(OBJEXT): $(hdrdir)/ruby.h
 string.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+string.$(OBJEXT): {$(VPATH)}assert.h
 string.$(OBJEXT): {$(VPATH)}config.h
 string.$(OBJEXT): {$(VPATH)}crypt.h
 string.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -2917,6 +2945,7 @@ struct.$(OBJEXT): $(CCAN_DIR)/list/list.h
 struct.$(OBJEXT): $(CCAN_DIR)/str/str.h
 struct.$(OBJEXT): $(hdrdir)/ruby.h
 struct.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+struct.$(OBJEXT): {$(VPATH)}assert.h
 struct.$(OBJEXT): {$(VPATH)}config.h
 struct.$(OBJEXT): {$(VPATH)}defines.h
 struct.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2942,6 +2971,7 @@ struct.$(OBJEXT): {$(VPATH)}vm_debug.h
 struct.$(OBJEXT): {$(VPATH)}vm_opts.h
 symbol.$(OBJEXT): $(hdrdir)/ruby.h
 symbol.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+symbol.$(OBJEXT): {$(VPATH)}assert.h
 symbol.$(OBJEXT): {$(VPATH)}config.h
 symbol.$(OBJEXT): {$(VPATH)}defines.h
 symbol.$(OBJEXT): {$(VPATH)}encoding.h
@@ -2969,6 +2999,7 @@ thread.$(OBJEXT): $(CCAN_DIR)/list/list.h
 thread.$(OBJEXT): $(CCAN_DIR)/str/str.h
 thread.$(OBJEXT): $(hdrdir)/ruby.h
 thread.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+thread.$(OBJEXT): {$(VPATH)}assert.h
 thread.$(OBJEXT): {$(VPATH)}config.h
 thread.$(OBJEXT): {$(VPATH)}debug.h
 thread.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -3035,6 +3066,7 @@ transcode.$(OBJEXT): {$(VPATH)}transcode.c
 transcode.$(OBJEXT): {$(VPATH)}transcode_data.h
 transient_heap.$(OBJEXT): $(hdrdir)/ruby.h
 transient_heap.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+transient_heap.$(OBJEXT): {$(VPATH)}assert.h
 transient_heap.$(OBJEXT): {$(VPATH)}config.h
 transient_heap.$(OBJEXT): {$(VPATH)}debug.h
 transient_heap.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -3072,6 +3104,7 @@ variable.$(OBJEXT): $(CCAN_DIR)/list/list.h
 variable.$(OBJEXT): $(CCAN_DIR)/str/str.h
 variable.$(OBJEXT): $(hdrdir)/ruby.h
 variable.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+variable.$(OBJEXT): {$(VPATH)}assert.h
 variable.$(OBJEXT): {$(VPATH)}config.h
 variable.$(OBJEXT): {$(VPATH)}constant.h
 variable.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -3107,6 +3140,7 @@ version.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 version.$(OBJEXT): $(hdrdir)/ruby/version.h
 version.$(OBJEXT): $(top_srcdir)/revision.h
 version.$(OBJEXT): $(top_srcdir)/version.h
+version.$(OBJEXT): {$(VPATH)}assert.h
 version.$(OBJEXT): {$(VPATH)}config.h
 version.$(OBJEXT): {$(VPATH)}debug_counter.h
 version.$(OBJEXT): {$(VPATH)}defines.h
@@ -3132,6 +3166,7 @@ vm.$(OBJEXT): $(CCAN_DIR)/list/list.h
 vm.$(OBJEXT): $(CCAN_DIR)/str/str.h
 vm.$(OBJEXT): $(hdrdir)/ruby.h
 vm.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+vm.$(OBJEXT): {$(VPATH)}assert.h
 vm.$(OBJEXT): {$(VPATH)}config.h
 vm.$(OBJEXT): {$(VPATH)}constant.h
 vm.$(OBJEXT): {$(VPATH)}debug_counter.h
@@ -3185,6 +3220,7 @@ vm_backtrace.$(OBJEXT): $(CCAN_DIR)/list/list.h
 vm_backtrace.$(OBJEXT): $(CCAN_DIR)/str/str.h
 vm_backtrace.$(OBJEXT): $(hdrdir)/ruby.h
 vm_backtrace.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+vm_backtrace.$(OBJEXT): {$(VPATH)}assert.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}config.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}debug.h
 vm_backtrace.$(OBJEXT): {$(VPATH)}defines.h
@@ -3217,6 +3253,7 @@ vm_dump.$(OBJEXT): $(CCAN_DIR)/str/str.h
 vm_dump.$(OBJEXT): $(hdrdir)/ruby.h
 vm_dump.$(OBJEXT): $(hdrdir)/ruby/ruby.h
 vm_dump.$(OBJEXT): {$(VPATH)}addr2line.h
+vm_dump.$(OBJEXT): {$(VPATH)}assert.h
 vm_dump.$(OBJEXT): {$(VPATH)}config.h
 vm_dump.$(OBJEXT): {$(VPATH)}defines.h
 vm_dump.$(OBJEXT): {$(VPATH)}encoding.h
@@ -3247,6 +3284,7 @@ vm_trace.$(OBJEXT): $(CCAN_DIR)/list/list.h
 vm_trace.$(OBJEXT): $(CCAN_DIR)/str/str.h
 vm_trace.$(OBJEXT): $(hdrdir)/ruby.h
 vm_trace.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+vm_trace.$(OBJEXT): {$(VPATH)}assert.h
 vm_trace.$(OBJEXT): {$(VPATH)}config.h
 vm_trace.$(OBJEXT): {$(VPATH)}debug.h
 vm_trace.$(OBJEXT): {$(VPATH)}debug_counter.h
diff --git a/ext/coverage/depend b/ext/coverage/depend
index 6ae027aec8..ad8c071fbe 100644
--- a/ext/coverage/depend
+++ b/ext/coverage/depend
@@ -14,6 +14,7 @@ $(OBJS): $(HDRS) $(ruby_headers) \
 coverage.o: $(RUBY_EXTCONF_H)
 coverage.o: $(arch_hdrdir)/ruby/config.h
 coverage.o: $(hdrdir)/ruby.h
+coverage.o: $(hdrdir)/ruby/assert.h
 coverage.o: $(hdrdir)/ruby/backward.h
 coverage.o: $(hdrdir)/ruby/defines.h
 coverage.o: $(hdrdir)/ruby/encoding.h
diff --git a/ext/objspace/depend b/ext/objspace/depend
index 060b863d04..32157bee2f 100644
--- a/ext/objspace/depend
+++ b/ext/objspace/depend
@@ -42,6 +42,7 @@ objspace.o: {$(VPATH)}id.h
 objspace_dump.o: $(RUBY_EXTCONF_H)
 objspace_dump.o: $(arch_hdrdir)/ruby/config.h
 objspace_dump.o: $(hdrdir)/ruby.h
+objspace_dump.o: $(hdrdir)/ruby/assert.h
 objspace_dump.o: $(hdrdir)/ruby/backward.h
 objspace_dump.o: $(hdrdir)/ruby/debug.h
 objspace_dump.o: $(hdrdir)/ruby/defines.h
diff --git a/include/ruby/assert.h b/include/ruby/assert.h
new file mode 100644
index 0000000000..5ef866ac9e
--- /dev/null
+++ b/include/ruby/assert.h
@@ -0,0 +1,49 @@
+#ifndef RUBY_ASSERT_H
+#define RUBY_ASSERT_H
+
+#if defined(__cplusplus)
+extern "C" {
+#if 0
+} /* satisfy cc-mode */
+#endif
+#endif
+
+NORETURN(void rb_assert_failure(const char *, int, const char *, const char *));
+#ifdef RUBY_FUNCTION_NAME_STRING
+# define RUBY_ASSERT_FAIL(expr) \
+    rb_assert_failure(__FILE__, __LINE__, RUBY_FUNCTION_NAME_STRING, expr)
+#else
+# define RUBY_ASSERT_FAIL(expr) \
+    rb_assert_failure(__FILE__, __LINE__, NULL, expr)
+#endif
+#define RUBY_ASSERT_MESG(expr, mesg) \
+    ((expr) ? (void)0 : RUBY_ASSERT_FAIL(mesg))
+#ifdef HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P
+# define RUBY_ASSERT_MESG_WHEN(cond, expr, mesg) \
+    __builtin_choose_expr( \
+	__builtin_constant_p(cond), \
+	__builtin_choose_expr(cond, RUBY_ASSERT_MESG(expr, mesg), (void)0), \
+	RUBY_ASSERT_MESG(!(cond) || (expr), mesg))
+#else
+# define RUBY_ASSERT_MESG_WHEN(cond, expr, mesg) \
+    RUBY_ASSERT_MESG(!(cond) || (expr), mesg)
+#endif
+#define RUBY_ASSERT(expr) RUBY_ASSERT_MESG_WHEN(!RUBY_NDEBUG+0, expr, #expr)
+#define RUBY_ASSERT_WHEN(cond, expr) RUBY_ASSERT_MESG_WHEN(cond, expr, #expr)
+
+#ifndef RUBY_NDEBUG
+# ifdef NDEBUG
+#   define RUBY_NDEBUG 1
+# else
+#   define RUBY_NDEBUG 0
+# endif
+#endif
+
+#if defined(__cplusplus)
+#if 0
+{ /* satisfy cc-mode */
+#endif
+}  /* extern "C" { */
+#endif
+
+#endif
diff --git a/ruby_assert.h b/ruby_assert.h
index 185d2e5f5f..139256fed8 100644
--- a/ruby_assert.h
+++ b/ruby_assert.h
@@ -1,37 +1,4 @@
-#ifndef RUBY_ASSERT_H
-#define RUBY_ASSERT_H
-
-#include "ruby/ruby.h"
-
-#if defined(__cplusplus)
-extern "C" {
-#if 0
-} /* satisfy cc-mode */
-#endif
-#endif
-
-NORETURN(void rb_assert_failure(const char *, int, const char *, const char *));
-#ifdef RUBY_FUNCTION_NAME_STRING
-# define RUBY_ASSERT_FAIL(expr) \
-    rb_assert_failure(__FILE__, __LINE__, RUBY_FUNCTION_NAME_STRING, expr)
-#else
-# define RUBY_ASSERT_FAIL(expr) \
-    rb_assert_failure(__FILE__, __LINE__, NULL, expr)
-#endif
-#define RUBY_ASSERT_MESG(expr, mesg) \
-    ((expr) ? (void)0 : RUBY_ASSERT_FAIL(mesg))
-#ifdef HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P
-# define RUBY_ASSERT_MESG_WHEN(cond, expr, mesg) \
-    __builtin_choose_expr( \
-	__builtin_constant_p(cond), \
-	__builtin_choose_expr(cond, RUBY_ASSERT_MESG(expr, mesg), (void)0), \
-	RUBY_ASSERT_MESG(!(cond) || (expr), mesg))
-#else
-# define RUBY_ASSERT_MESG_WHEN(cond, expr, mesg) \
-    RUBY_ASSERT_MESG(!(cond) || (expr), mesg)
-#endif
-#define RUBY_ASSERT(expr) RUBY_ASSERT_MESG_WHEN(!RUBY_NDEBUG+0, expr, #expr)
-#define RUBY_ASSERT_WHEN(cond, expr) RUBY_ASSERT_MESG_WHEN(cond, expr, #expr)
+#include "ruby/assert.h"
 
 #if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L)
 /* C89 compilers are required to support strings of only 509 chars. */
@@ -41,20 +8,3 @@ NORETURN(void rb_assert_failure(const char *, int, const char *, const char *));
 #undef assert
 #define assert RUBY_ASSERT
 #endif
-
-#ifndef RUBY_NDEBUG
-# ifdef NDEBUG
-#   define RUBY_NDEBUG 1
-# else
-#   define RUBY_NDEBUG 0
-# endif
-#endif
-
-#if defined(__cplusplus)
-#if 0
-{ /* satisfy cc-mode */
-#endif
-}  /* extern "C" { */
-#endif
-
-#endif