diff --git a/convert.c b/convert.c
index 80f114b2e2..552707e8e6 100644
--- a/convert.c
+++ b/convert.c
@@ -326,14 +326,14 @@ static int read_convert_config(const char *var, const char *value)
 
 	if (!strcmp("smudge", ep)) {
 		if (!value)
-			return error("%s: lacks value", var);
+			return config_error_nonbool(var);
 		drv->smudge = strdup(value);
 		return 0;
 	}
 
 	if (!strcmp("clean", ep)) {
 		if (!value)
-			return error("%s: lacks value", var);
+			return config_error_nonbool(var);
 		drv->clean = strdup(value);
 		return 0;
 	}