diff --git a/port/shim/PR/gbi.h b/port/shim/PR/gbi.h
index ca4a6f92..99e5a2d2 100644
--- a/port/shim/PR/gbi.h
+++ b/port/shim/PR/gbi.h
@@ -136,5 +136,21 @@ typedef union {
 
 #define Gfx Gfx_le
 
+/*
+ * The gDP* display-list macros in the real gbi.h use _SHIFTL/_SHIFTR, which
+ * the N64 headers define in PR/mbi.h. A port TU that includes <PR/gbi.h>
+ * without <ultra64.h> (e.g. port/src/video.c) never reaches mbi.h; on Linux
+ * no other header in its include chain pulls it in, so the gDP* calls expand
+ * to implicit _SHIFTL()/_SHIFTR() function calls and fail to link (D402).
+ * Define them if absent. Guarded so a TU that also reaches mbi.h keeps
+ * mbi.h's own definitions.
+ */
+#ifndef _SHIFTL
+#    define _SHIFTL(v, s, w) ((u32)(((u32)(v) & ((0x01 << (w)) - 1)) << (s)))
+#endif
+#ifndef _SHIFTR
+#    define _SHIFTR(v, s, w) ((u32)(((u32)(v) >> (s)) & ((0x01 << (w)) - 1)))
+#endif
+
 #endif /* defined(PORT) */
 #endif /* _PORT_SHIM_GBI_H_ */
diff --git a/port/shim/PR/ucode.h b/port/shim/PR/ucode.h
index a891cec2..998cf993 100644
--- a/port/shim/PR/ucode.h
+++ b/port/shim/PR/ucode.h
@@ -13,7 +13,18 @@
 
 #if defined(PORT)
 #    include "include/PR/ucode.h"
-#    include "pc_protos.h"
+#    /* D402 (Linux build): a TU that includes <bondconstants.h> before
+#     * <ultra64.h> (e.g. port/src/optionsoverlay.c) sets src/bondconstants.h's
+#     * include-guard, then that header's own top `#include <ultra64.h>` reaches
+#     * this pc_protos.h -> bondtypes.h -> bondconstants.h chain while
+#     * src/bondconstants.h is still mid-parse (its ITEM_IDS/ACT_TYPE/... are
+#     * defined only later in the file). glibc GCC rejects the half-defined
+#     * types hard (MinGW tolerated it, so this only surfaced on Linux). The
+#     * bondconstants.h shim sets _PORT_DEFER_PC_PROTOS around that pass so the
+#     * D38 prototypes are pulled in only once, after the constants are whole. */
+#    if !defined(_PORT_DEFER_PC_PROTOS)
+#        include "pc_protos.h"
+#    endif
 #else
 #    include <PR/ucode.h>
 #endif
diff --git a/port/shim/bondconstants.h b/port/shim/bondconstants.h
index c876c076..5a75ef0b 100644
--- a/port/shim/bondconstants.h
+++ b/port/shim/bondconstants.h
@@ -21,7 +21,21 @@
  * Inert in the N64 build (no -DPORT): pure pass-through.
  */
 #if defined(PORT)
+/* D402 (Linux build): parse the PR base headers first, but tell the PR/ucode.h
+ * shim to defer pc_protos.h for this pass. pc_protos.h reaches bondtypes.h,
+ * which needs the bondconstants.h types (ITEM_IDS, ACT_TYPE, ...) that are only
+ * defined later in src/bondconstants.h. Without this, a TU that includes
+ * <bondconstants.h> before <ultra64.h> re-enters the still-parsing
+ * src/bondconstants.h (guard already set) from bondtypes.h and glibc GCC
+ * rejects the half-defined types (MinGW tolerated it). We finish
+ * src/bondconstants.h below and then pull pc_protos.h so the D38 prototypes
+ * are still seen exactly once. */
+#    define _PORT_DEFER_PC_PROTOS
+#    include <ultra64.h>
+#    undef _PORT_DEFER_PC_PROTOS
+
 #include "src/bondconstants.h"
+#include "pc_protos.h"
 
 /*
  * D38: src/bondconstants.h defines ntohl()/ntohs() as function-like macros