diff --git a/configure b/configure
index 5df1edf6a37..f4743c27531 100755
--- a/configure
+++ b/configure
@@ -134,7 +134,7 @@ BEGIN {
     values["LITERAL_WHITESPACE"] = " "
     values["LITERAL_DOLLAR"] = "$"
 }
-/^[_A-Z0-9.]+ *\+?=/ {
+/^[_A-Z0-9.]+[ \t]*\+?=/ {
     valStart = index($0, "=") + 1
 
     append = 0