diff --git a/dir.c b/dir.c
index a090b9f38c..ee58d9c656 100644
--- a/dir.c
+++ b/dir.c
@@ -2948,7 +2948,7 @@ dir_glob_option_base(VALUE base)
 static int
 dir_glob_option_sort(VALUE sort)
 {
-    return (rb_bool_expected(sort, "sort") ? 0 : FNM_GLOB_NOSORT);
+    return (rb_bool_expected(sort, "sort", TRUE) ? 0 : FNM_GLOB_NOSORT);
 }
 
 static VALUE
diff --git a/error.c b/error.c
index c420aaca3c..35e797f5b9 100644
--- a/error.c
+++ b/error.c
@@ -1273,7 +1273,7 @@ check_highlight_keyword(VALUE opt, int auto_tty_detect)
 
         switch (highlight) {
           default:
-            rb_bool_expected(highlight, "highlight");
+            rb_bool_expected(highlight, "highlight", TRUE);
             UNREACHABLE;
           case Qtrue: case Qfalse: case Qnil: break;
         }
diff --git a/internal/object.h b/internal/object.h
index f560fb7f9f..88f3a44bc6 100644
--- a/internal/object.h
+++ b/internal/object.h
@@ -22,7 +22,7 @@ double rb_num_to_dbl(VALUE val);
 VALUE rb_obj_dig(int argc, VALUE *argv, VALUE self, VALUE notfound);
 VALUE rb_immutable_obj_clone(int, VALUE *, VALUE);
 VALUE rb_check_convert_type_with_id(VALUE,int,const char*,ID);
-int rb_bool_expected(VALUE, const char *);
+int rb_bool_expected(VALUE, const char *, int raise);
 static inline void RBASIC_CLEAR_CLASS(VALUE obj);
 static inline void RBASIC_SET_CLASS_RAW(VALUE obj, VALUE klass);
 static inline void RBASIC_SET_CLASS(VALUE obj, VALUE klass);
diff --git a/io.c b/io.c
index fc1a5d8110..a8326fcbcf 100644
--- a/io.c
+++ b/io.c
@@ -3385,7 +3385,7 @@ io_read_nonblock(rb_execution_context_t *ec, VALUE io, VALUE length, VALUE str,
     }
 
     shrinkable = io_setstrbuf(&str, len);
-    rb_bool_expected(ex, "exception");
+    rb_bool_expected(ex, "exception", TRUE);
 
     GetOpenFile(io, fptr);
     rb_io_check_byte_readable(fptr);
@@ -3433,7 +3433,7 @@ io_write_nonblock(rb_execution_context_t *ec, VALUE io, VALUE str, VALUE ex)
 
     if (!RB_TYPE_P(str, T_STRING))
 	str = rb_obj_as_string(str);
-    rb_bool_expected(ex, "exception");
+    rb_bool_expected(ex, "exception", TRUE);
 
     io = GetWriteIO(io);
     GetOpenFile(io, fptr);
diff --git a/object.c b/object.c
index c7375f0c56..6a7b2cbf23 100644
--- a/object.c
+++ b/object.c
@@ -3158,16 +3158,22 @@ rb_check_integer_type(VALUE val)
 }
 
 int
-rb_bool_expected(VALUE obj, const char *flagname)
+rb_bool_expected(VALUE obj, const char *flagname, int raise)
 {
     switch (obj) {
-      case Qtrue: case Qfalse:
-        break;
-      default:
-        rb_raise(rb_eArgError, "expected true or false as %s: %+"PRIsVALUE,
-                 flagname, obj);
+      case Qtrue:
+        return TRUE;
+      case Qfalse:
+        return FALSE;
+      default: {
+        static const char message[] = "expected true or false as %s: %+"PRIsVALUE;
+        if (raise) {
+            rb_raise(rb_eArgError, message, flagname, obj);
+        }
+        rb_warning(message, flagname, obj);
+        return !NIL_P(obj);
+      }
     }
-    return obj != Qfalse;
 }
 
 int
@@ -3176,7 +3182,7 @@ rb_opts_exception_p(VALUE opts, int default_value)
     static const ID kwds[1] = {idException};
     VALUE exception;
     if (rb_get_kwargs(opts, kwds, 0, 1, &exception))
-        return rb_bool_expected(exception, "exception");
+        return rb_bool_expected(exception, "exception", TRUE);
     return default_value;
 }
 
@@ -3562,7 +3568,7 @@ rb_f_float1(rb_execution_context_t *ec, VALUE obj, VALUE arg)
 static VALUE
 rb_f_float(rb_execution_context_t *ec, VALUE obj, VALUE arg, VALUE opts)
 {
-    int exception = rb_bool_expected(opts, "exception");
+    int exception = rb_bool_expected(opts, "exception", TRUE);
     return rb_convert_to_float(arg, exception);
 }
 
diff --git a/process.c b/process.c
index 9568399f93..53727ab116 100644
--- a/process.c
+++ b/process.c
@@ -2210,7 +2210,7 @@ rb_execarg_addopt_rlimit(struct rb_execarg *eargp, int rtype, VALUE val)
 }
 #endif
 
-#define TO_BOOL(val, name) NIL_P(val) ? 0 : rb_bool_expected((val), name)
+#define TO_BOOL(val, name) (NIL_P(val) ? 0 : rb_bool_expected((val), name, TRUE))
 int
 rb_execarg_addopt(VALUE execarg_obj, VALUE key, VALUE val)
 {