diff --git a/src/getchar.c b/src/getchar.c
index a8778e0..4f5ea46 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -2037,7 +2037,7 @@
 	if (argvars[0].v_type == VAR_UNKNOWN)
 	    // getchar(): blocking wait.
 	    n = plain_vgetc();
-	else if (tv_get_number_chk(&argvars[0], &error) == 1)
+	else if (tv_get_bool_chk(&argvars[0], &error))
 	    // getchar(1): only check if char avail
 	    n = vpeekc_any();
 	else if (error || vpeekc_any() == NUL)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 7303db9..3453f44 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1505,6 +1505,10 @@
   bwipe Xtestfile1 Xtestfile2
 enddef
 
+def Test_getchar()
+  assert_equal(0, getchar(true))
+enddef
+
 def Fibonacci(n: number): number
   if n < 2
     return n
diff --git a/src/version.c b/src/version.c
index 9a58f11..7ce5eb2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1603,
+/**/
     1602,
 /**/
     1601,