diff --git a/src/testing.c b/src/testing.c
index 3e6ba8e..ac9beea 100644
--- a/src/testing.c
+++ b/src/testing.c
@@ -222,7 +222,7 @@
     int		error = FALSE;
     garray_T	ga;
 
-    if (argvars[0].v_type == VAR_SPECIAL
+    if (argvars[0].v_type == VAR_BOOL
 	    && argvars[0].vval.v_number == (isTrue ? VVAL_TRUE : VVAL_FALSE))
 	return 0;
     if (argvars[0].v_type != VAR_NUMBER
@@ -760,6 +760,7 @@
 	case VAR_UNKNOWN:
 	case VAR_NUMBER:
 	case VAR_FLOAT:
+	case VAR_BOOL:
 	case VAR_SPECIAL:
 	case VAR_STRING:
 	    break;