diff --git a/color.c b/color.c
index 62977f4..8f07fc9 100644
--- a/color.c
+++ b/color.c
@@ -138,6 +138,9 @@
 			goto auto_color;
 	}
 
+	if (!var)
+		return -1;
+
 	/* Missing or explicit false to turn off colorization */
 	if (!git_config_bool(var, value))
 		return 0;