diff --git a/cmd/wcc/type.c b/cmd/wcc/type.c
index ebafc41d..671118d4 100644
--- a/cmd/wcc/type.c
+++ b/cmd/wcc/type.c
@@ -64,6 +64,7 @@ typesinit(Arena *a)
 	 * Size sourced from the slice SSoT (type_slice) so str and []u8 can
 	 * never drift; no second hardcoded 24. */
 	ty_str    = prim(a, TY_STR,    "str",    type_slice(a, ty_u8)->size, 8);
+	ty_str->sub = ty_u8;	/* str IS []u8: element is u8 (Phase 2 F1) */
 	ty_err    = prim(a, TY_ERR,    "<err>",   0, 1);
 	ty_never  = prim(a, TY_NEVER,  "never",   0, 1);
 	/* #29: predeclared `type nomem = !void;`. NAMED so variant_match
diff --git a/lib/ww/typ.ww b/lib/ww/typ.ww
index ad492bbc..60096c80 100644
--- a/lib/ww/typ.ww
+++ b/lib/ww/typ.ww
@@ -219,6 +219,7 @@ export fn typesinit(c: *tctx) void = {
 	// cgdot mirror); retained here as a local until that lands.
 	let u8slice: *tinfo = typeslice(c.tyu8);
 	c.tystr    = prim(tykind.TY_STR,  "str",  u8slice.size, 8u64);
+	c.tystr.sub = c.tyu8;	// str IS []u8: element is u8 (Phase 2 F1)
 	c.tyerr    = prim(tykind.TY_ERR,  "<err>", 0u64, 1u64);
 	c.tynever  = prim(tykind.TY_NEVER, "never", 0u64, 1u64);
 
diff --git a/selfhost/cmd/w6c/main.combined.ww b/selfhost/cmd/w6c/main.combined.ww
index 23723cd3..0c2e6ed6 100644
--- a/selfhost/cmd/w6c/main.combined.ww
+++ b/selfhost/cmd/w6c/main.combined.ww
@@ -6549,6 +6549,7 @@ export fn typesinit(c: *tctx) void = {
 	// cgdot mirror); retained here as a local until that lands.
 	let u8slice: *tinfo = typeslice(c.tyu8);
 	c.tystr    = prim(tykind.TY_STR,  "str",  u8slice.size, 8u64);
+	c.tystr.sub = c.tyu8;	// str IS []u8: element is u8 (Phase 2 F1)
 	c.tyerr    = prim(tykind.TY_ERR,  "<err>", 0u64, 1u64);
 	c.tynever  = prim(tykind.TY_NEVER, "never", 0u64, 1u64);
 
diff --git a/selfhost/cmd/wwdump/main.combined.ww b/selfhost/cmd/wwdump/main.combined.ww
index e067c071..b94eab57 100644
--- a/selfhost/cmd/wwdump/main.combined.ww
+++ b/selfhost/cmd/wwdump/main.combined.ww
@@ -6549,6 +6549,7 @@ export fn typesinit(c: *tctx) void = {
 	// cgdot mirror); retained here as a local until that lands.
 	let u8slice: *tinfo = typeslice(c.tyu8);
 	c.tystr    = prim(tykind.TY_STR,  "str",  u8slice.size, 8u64);
+	c.tystr.sub = c.tyu8;	// str IS []u8: element is u8 (Phase 2 F1)
 	c.tyerr    = prim(tykind.TY_ERR,  "<err>", 0u64, 1u64);
 	c.tynever  = prim(tykind.TY_NEVER, "never", 0u64, 1u64);