diff --git a/lib/std/Build/Step/ConfigHeader.zig b/lib/std/Build/Step/ConfigHeader.zig
index e1a7e9f63f1bcdc75bab028e0a153b92f5b90f24..4174d398b46ed1294ab90c36c02604d7fd1ffcff 100644
--- a/lib/std/Build/Step/ConfigHeader.zig
+++ b/lib/std/Build/Step/ConfigHeader.zig
@@ -286,7 +286,7 @@ fn render_autoconf(
             try output.appendSlice("\n");
             continue;
         }
-        const name = it.rest();
+        const name = it.next().?;
         const index = values.getIndex(name) orelse {
             try step.addError("{s}:{d}: error: unspecified config header value: '{s}'", .{
                 src_path, line_index + 1, name,
diff --git a/test/standalone/config_header/build.zig b/test/standalone/config_header/build.zig
index 0268b642a7281103a820204a46a3c1f035f6580b..fba2613c5a7f936d5d45ab3e596bbf4cd4147e08 100644
--- a/test/standalone/config_header/build.zig
+++ b/test/standalone/config_header/build.zig
@@ -12,6 +12,11 @@ pub fn build(b: *std.Build) void {
             .SOME_TEN = 10,
             .SOME_ENUM_LITERAL = .@"test",
             .SOME_STRING = "test",
+
+            .PREFIX_SPACE = null,
+            .PREFIX_TAB = null,
+            .POSTFIX_SPACE = null,
+            .POSTFIX_TAB = null,
         },
     );
 
diff --git a/test/standalone/config_header/config.h b/test/standalone/config_header/config.h
index aa9a9a707cb52a283b7c1f0f077fad281656315d..298aeac344422ee19834abeb980e8a594ccb2214 100644
--- a/test/standalone/config_header/config.h
+++ b/test/standalone/config_header/config.h
@@ -15,3 +15,8 @@ int foo();
 // Used twice
 #define SOME_TRUE 1
 
+/* #undef PREFIX_SPACE */
+/* #undef PREFIX_TAB */
+/* #undef POSTFIX_SPACE */
+/* #undef POSTFIX_TAB */
+
diff --git a/test/standalone/config_header/config.h.in b/test/standalone/config_header/config.h.in
index 4858d0879491859ec1b1cf441f01b3933d9fb782..b4cf3a47ea4e2c32bc103c2764b2e566ccbe5920 100644
--- a/test/standalone/config_header/config.h.in
+++ b/test/standalone/config_header/config.h.in
@@ -13,3 +13,8 @@ int foo();
 
 // Used twice
 #undef SOME_TRUE
+
+#undef PREFIX_SPACE
+#undef	PREFIX_TAB
+#undef POSTFIX_SPACE 
+#undef POSTFIX_TAB