diff --git a/complex.c b/complex.c
index c9048409a1..eb0435bed1 100644
--- a/complex.c
+++ b/complex.c
@@ -419,7 +419,7 @@ static VALUE nucomp_s_convert(int argc, VALUE *argv, VALUE klass);
 
 /*
  * call-seq:
- *    Complex(x[, y], exception: false)  ->  numeric
+ *    Complex(x[, y], exception: false)  ->  numeric or nil
  *
  * Returns x+i*y;
  *
diff --git a/object.c b/object.c
index 31caea714f..af8f8aee38 100644
--- a/object.c
+++ b/object.c
@@ -3221,7 +3221,7 @@ opts_exception_p(VALUE opts)
 
 /*
  *  call-seq:
- *     Integer(arg, base=0, exception: true)    -> integer
+ *     Integer(arg, base=0, exception: true)    -> integer or nil
  *
  *  Converts <i>arg</i> to an <code>Integer</code>.
  *  Numeric types are converted directly (with floating point numbers
@@ -3583,7 +3583,7 @@ rb_Float(VALUE val)
 
 /*
  *  call-seq:
- *     Float(arg, exception: true)    -> float
+ *     Float(arg, exception: true)    -> float or nil
  *
  *  Returns <i>arg</i> converted to a float. Numeric types are converted
  *  directly, and with exception to string and nil the rest are converted using <i>arg</i>.to_f.
diff --git a/rational.c b/rational.c
index af990b9c46..089f5d54f1 100644
--- a/rational.c
+++ b/rational.c
@@ -529,8 +529,8 @@ static VALUE nurat_s_convert(int argc, VALUE *argv, VALUE klass);
 
 /*
  * call-seq:
- *    Rational(x, y, exception: true)  ->  rational
- *    Rational(arg, exception: true)   ->  rational
+ *    Rational(x, y, exception: true)  ->  rational or nil
+ *    Rational(arg, exception: true)   ->  rational or nil
  *
  * Returns +x/y+ or +arg+ as a Rational.
  *