diff --git a/configure.ac b/configure.ac
index 4cab71857..ed3405d37 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@ SDL_VERSION=$SDL_MAJOR_VERSION.$SDL_MINOR_VERSION.$SDL_MICRO_VERSION
 
 SDL_BINARY_AGE=`expr $SDL_MINOR_VERSION \* 100 + $SDL_MICRO_VERSION`
 AS_CASE(["$SDL_MINOR_VERSION"],
-  [*[02468]],
+  [*@<:@02468@:>@],
     dnl Stable branch, 2.24.1 -> libSDL2-2.0.so.0.2400.1
     [SDL_INTERFACE_AGE="$SDL_MICRO_VERSION"],
   [*],